ls
this is the most basic of all basic commands to know.
ls lists the contents of a directory, if you type just `ls`
it will list the contents of the current directory, but it can also
be used as `ls /way/to/some/other/dir/` to list the contents of
some other directory, ls has alot of arguments which are:
-a, --all
do not hide entries starting with .
-A, --almost-all
do not list implied . and ..
-b, --escape
print octal escapes for nongraphic characters
--block-size=SIZE
use SIZE-byte blocks
-B, --ignore-backups
do not list implied entries ending with ~
-c
sort by change time; with -l: show ctime
-C
list entries by columns
--color[=WHEN]
control whether color is used to distinguish file
types. WHEN may be `never', `always', or `auto'
-d, --directory
list directory entries instead of contents
-D, --dired
generate output designed for Emacs' dired mode
-f
do not sort, enable -aU, disable -lst
-F, --classify
append indicator (one of */=@|) to entries
--format=WORD
across -x, commas -m, horizontal -x, long -l,
single-column -1, verbose -l, vertical -C
--full-time
list both full date and full time
-g
(ignored)
-G, --no-group
inhibit display of group information
-h, --human-readable
print sizes in human readable format (e.g., 1K 234M 2G)
-H, --si
likewise, but use powers of 1000 not 1024
--indicator-style=WORD
append indicator with style WORD to entry names:
none (default), classify (-F), file-type (-p)
-i, --inode
print index number of each file
-I, --ignore=PATTERN
do not list implied entries matching shell PATTERN
-k, --kilobytes
like --block-size=1024
-l
use a long listing format
-L, --dereference
list entries pointed to by symbolic links
-m
fill width with a comma separated list of entries
-n, --numeric-uid-gid
list numeric UIDs and GIDs instead of names
-N, --literal
print raw entry names (don't treat e.g. control
characters specially)
-o
use long listing format without group info
-p, --file-type
append indicator (one of /=@|) to entries
-q, --hide-control-chars
print ? instead of non graphic characters
--show-control-chars
show non graphic characters as-is (default)
-Q, --quote-name
enclose entry names in double quotes
--quoting-style=WORD
use quoting style WORD for entry names:
literal, shell, shell-always, c, escape
-r, --reverse
reverse order while sorting
-R, --recursive
list subdirectories recursively
-s, --size
print size of each file, in blocks
-S
sort by file size
--sort=WORD
extension -X, none -U, size -S, time -t, version -v
status -c, time -t, atime -u, access -u, use -u
--time=WORD
show time as WORD instead of modification time:
atime, access, use, ctime or status; use
specified time as sort key if --sort=time
-t
sort by modification time
-T, --tabsize=COLS
assume tab stops at each COLS instead of 8
-u
sort by last access time; with -l: show atime
-U
do not sort; list entries in directory order
-v
sort by version
-w, --width=COLS
assume screen width instead of current value
-x
list entries by lines instead of by columns
-X
sort alphabetically by entry extension
-1
list one file per line
--help display this help and exit
--version output version information and exit
Some good examples are:
ls -la
ls -laF
ls -laF --color
ls -d */
Also see earlier in this tutorial about the `alias` command
-------------------------------------------------------------------------------
lsattr
list attributes, this command lists a files file system attributes.
For more info see: man lsattr
-------------------------------------------------------------------------------
lsmod
list modules, lists all loaded modules with a very brief information.
-------------------------------------------------------------------------------
lsof
list open files, this is a huge command, so if you really
wanna find out more about this interesting command you will have
to read the manual page for it.
But here's an example of use for it:
lsof -p 1
Which would be the same as:
lsof -p `pidof init`
Here's another example:
lsof -p `pidof httpd | sed 's/ /,/g'`
The "-p" means that the following argument will be a PID (Process ID).
The "sed" part in the later example replaces any spaces with "," since
lsof doesnt want spaces between the pids, as the output of pidof gives.
For more info see: man lsof
-------------------------------------------------------------------------------
lynx
lynx is a console based world wide web browser, that has alot of
arguments with which it can be executed, but it basicly works like
this: lynx <url>
If you press 'g' while in lynx you can type in the url where you
wanna go, and if you press 'q' you quit lynx.
You search in text with lynx with '/' and move around with
the arrow keys and the TAB key.
A tips is that lynx works as a file manager, as this: lynx </path/>
A good usage for lynx is that you can use it as direct downloader,
like this: lynx -souce ftp://ftp.bogus.com/foo/bar.tar.gz > bar.tar.gz
For more help or information do: lynx --help
Or: man lynx
-------------------------------------------------------------------------------
mail
mail is most commonly used to just check your mail in the most
simple way by just typing `mail`, but it can also be used
with alot of arguments, I have personally never used
any arguments to the mail command, but if you wanna check
them out do: man mail
-------------------------------------------------------------------------------
man
manual pages, there are several different manual pages, say for example
the command exec, `man exec` should bring you little, while
`man 3 exec` should bring you the C function manual on exec.
The man pages traditional way of storing is:
man1 misc user commands
man2 C programming functions
man3 more C programming functions
man4 network related manuals
man5 system related files
man6 game manuals
man7 misc technical manuals
man8 misc superuser commands
man9 misc system/devices
I may be wrong about the category's there, but that's how it seems
to me.
Anyway, to bring up a manual page simply do: man <command>
or: man <number> <command>
-------------------------------------------------------------------------------
mc
midnight commander is a visual shell for *nix Operating Systems.
mc is quite large and has alot of arguments, I personally don't use
midnight commander at all, but if you wanna learn more about it
do: man mc
-------------------------------------------------------------------------------
mesg
mesg is a command with which you control if other users should
have write access to your terminal, as `wall` messages, `write`
or anything similar.
mesg y turns on the access for others to write to your terminal.
mesg n turns off the access for others to write to your terminal.
-------------------------------------------------------------------------------
mkdir
make directory, creates a directory, works as: mkdir [arguments] dir/
The arguments can be as follows:
-m, --mode=MODE see chmod's octal (numerical) modes
-p, --parents no error if existing, make parent
directories as needed
--verbose print a message for each created directory
--help display the help and exit
--version output version information and exit
mkdir is most commonly used as: mkdir <newdir>
-------------------------------------------------------------------------------
mknod
mknod is used to create special files, as devices.
mknod's syntax is this: mknod [arguments] <name> <type> [MAJOR MINOR]
It can be used with the following arguments:
-m, --mode=MODE
set permission mode (as in chmod), not 0666 - umask
--help
display this help and exit
--version
output version information and exit
MAJOR MINOR are forbidden for <type> p, else they must be used.
b create a block (buffered) special file
c, u create a character (unbuffered) special file
p create a FIFO
You need to know the devices major/minior number if you gonna use this
command, those are located in /usr/src/linux/Documentation/devices.txt
that comes with the kenrnel source.
The "char" is the minior and the number before the devices are the
major numbers so say that you wanna make a new /dev/null for some
reason, then you read the devices.txt and see this:
1 char Memory devices
1 = /dev/mem Physical memory access
2 = /dev/kmem Kernel virtual memory access
3 = /dev/null Null device
And so you make the null device like this:
mknod /dev/null b 1 3
Or if you wanna make a new /dev/scd device to support another
emulated scsi cdrom device. (there are 7 scd devices default)
So here's how you make another:
mknod /dev/scd8 b 11 8
This is not as hard at all .....
for more info: info mknod
or: man mknod
-------------------------------------------------------------------------------
modprobe
modprobe loads modules in a similar way as depmod.
See modprobe's manual page: man modprobe
-------------------------------------------------------------------------------
more
more is a command to display a files contents, it's very similar
to the `less` command.
See `less` and more's manual pages: man more
-------------------------------------------------------------------------------
mount
mount, mounts a media, that is to say that you make the contents
of say a hard drive visible to the system on some mountpoint,
ie. mount -t vfat /dev/hda1 /windows
This command would mount hda1 (the first harddrive's (hd a)
first partition (hda 1), as (-t <filesystem>) vfat which is
the windows native filesystem.
Linux native filesystem is ext2.
mount has ALOT of arguments, if you wanna read about them all
do: man mount
-------------------------------------------------------------------------------
mv
mv, moves a file or directory.
It works like this: mv [argument] <file-to-move> <new-name/location>
This is an example: mv /home/alien/bash.tutor /home/old/bash.tutor
Or just to rename a file: mv bash.tutor bash.file
mv can also be executed with alot of arguments, which are:
-b, --backup
make backup before removal
-f, --force
remove existing destinations, never prompt
-i, --interactive
prompt before overwrite
-S, --suffix=SUFFIX
override the usual backup suffix
-u, --update
move only older or brand new non-directories
-v, --verbose
explain what is being done
-V, --version-control=WORD
override the usual version control
--help
display the help and exit
--version
output version information and exit
Here's an example: mv -f /home/alien/bash.tutor /
This will by force mv the file to / (if you have write rights to /)
-------------------------------------------------------------------------------
nc / netcat
netcat is by default usually located in: /usr/lib/linuxconf/lib/
netcat is very useful in internet based shell scripts, since
it can listen on a socket or send to sockets, depending on the version.
the default netcat can as far as I know only send to sockets.
works basicly like this:
/usr/lib/linuxconf/lib/netcat --file <file> <ip> <port>
But can be executed with the following arguments:
--head <nb_lines>
--tail <nb_lines>
--send <file>
A tip is to make one or two links from /usr/lib/linuxconf/lib/netcat
to /usr/local/bin/netcat and perhaps /usr/local/bin/nc
-------------------------------------------------------------------------------
ncftp
ncftp is a very powerful ftp client.
ncftp has the following syntax: ncftp [arguments] <host>
If no arguments is given it will try to login as anonymous user
with an e-mail as password.
Most common non-anonymous usage is this: ncftp -u <username> <host>
The commands you will use the most once logged on to an ftp
is the following:
get <name> download a file
put <name> upload a file
ls list current directory
cd <dir-name> change directory
lls list local directory
lcd change local directory
If you want to read all ncftp's commands and arguments do: man ncftp
-------------------------------------------------------------------------------
ncftpget
ncftpget is a command line based ftp download client. It works
like this: ncftpget [arguments] <host> <local-dir> <remote-files>
ncftpget comes with ncftp, if you want to see all it's commands,
do: man ncftpget
-------------------------------------------------------------------------------
ncftpput
ncftpput is a command line based ftp upload client. It works
like this: ncftpput [arguments] <host> <remote-dir> <remote-files>
ncftpput comes with ncftp, if you want to see all it's commands,
do: man ncftpput
-------------------------------------------------------------------------------
netstat
netstat will show you the network connections to and from your computer
that's currently active, it can simply be used by typing `netcat`
or it can me used with it's arguments, if you wanna learn
more about this command, do: man netcat
-------------------------------------------------------------------------------
nice
nice is a command that can set the priority (cpu time) of a program
or a command, the prioretys can be from -20 which is max priority
to 19 which is the minimum priority.
nice works like this: nice [argument] <command> <argument>
The arguments "[argument]" for nice can be:
-ADJUST
increment priority by ADJUST first
-n, --adjustment=ADJUST
same as -ADJUST
--help
display the help and exit
--version
output version information and exit
Example: nice -n -20 make bzImage
This will make the kernel with as much CPU as it can.
This means this process has more rights then any other process.
Another example is: nice -n 19 zgv
This will give zgv absolutely lowest priority, and will there for
be the slowest moving processes on the system, as if it runs
with nice 19 and another process comes and wants more CPU power
then there is free, `zgv` will in this case give the other
process of it's own power.
-------------------------------------------------------------------------------
nmap
nmap is getting to come as default for some Linux distributions,
and is a port scanner, maybe the best port scanner there is.
nmap is used like this: nmap [arguments] <host / ip>
So say you want to port scan yourself you could do:
nmap 127.0.0.1
Or: nmap localhost
The most commonly used arguments to nmap is the '-sS' which
is a SYN scan, and will in most cases not reveal your IP
to the one that your scanning, BUT if the other side
has any kind of modern logging device as a fairly new
firewall or port logger your IP will be shown to him anyway.
The other perhaps next most common argument to use is the '-O'
argument, which will give you a good guess of what the remote
operating system is this function works the same as for
the operating system guess program `queso`.
Example: nmap -sS -O localhost > localhost.log
The '> localhost.log' part will put the outcome of the scan in a file
called localhost.log.
-------------------------------------------------------------------------------
ntpdate
ntpdate has no manual page nor any help page what I can found,
perhaps I'll write one if I'm bored some day .....
ntpdate will synchronize your computers system clock with an atomic
clock.
ntpdate's help usage gives this:
usage: ntpdate [-bBdqsv] [-a key#] [-e delay] [-k file] [-p samples]
[-o version#] [-r rate] [-t timeo] server ...
I only use it as: ntpdate <server>
Like this: ntpdate ntp.lth.se
-------------------------------------------------------------------------------
ntsys / ntsysv
runlevel confuration tool.
This tool lets you configure what services that should be
started with your runlevel, alteast ntsysv has a nice
ncurses interface that's easy to handle.
For moreinformation on this command do: man ntsys
Or: man ntsysv
Depending on your system.
-------------------------------------------------------------------------------
objdump
objdump is a quite large command, that allows you to dump objects
out of a binary file.
To dump all objects do: objdump --source <binary file>
For more info do: man objdump
-------------------------------------------------------------------------------
passwd
passwd is a little tool to set a password to a user account,
it basicly works like this: passwd [arguments] <username>
or if you just type `passwd` you will change your own password.
passwd can be sued with the following arguments:
-d, --delete delete the password for the named account
(root only)
-f, --force force operation
-k, --keep-tokens keep non-expired authentication tokens
-l, --lock lock the named account (root only)
-S, --status report password status on the named account
(root only)
--stdin read new tokens from stdin (root only)
-u, --unlock unlock the named account (root only)
Help options
-?, --help Show the help message
--usage Display brief usage message
You still need to do a: man passwd
-------------------------------------------------------------------------------
patch
patch simply works like this: patch <original-file> <patch-file>
A patch is done with the `diff` command as
this: diff file1 file2 > patchfile
So then to make file1 identical to file2: patch file1 patchfile
patch can however be used with a whole lot of arguments,
if you are interested do: man patch
Or: patch --help
-------------------------------------------------------------------------------
pidof
pidof simply gives the PID of a running process without you having
to use "ps", say that you want to find out what pid your init has,
(it will always be one for the init), then you do: pidof init
Or if you wanna find out which pids are used by the web server (httpd)
then you do: pidof httpd
So basically you find out the pids from the process name(s).
pidof has the following switches:
-s Single shot - this instructs the program to only return one pid.
-x Scripts too - this causes the program to also return process
id's of shells running the named scripts.
-o Tells pidof to omit processes with that process id.
The special pid %PPID can be used to name the parent process of
the pidof program, in other words the calling shell or shell
script.
For more info see: man pidof
-------------------------------------------------------------------------------
ping
ping is a pretty basic command, that will work
as: ping [arguments] <ip-or-host>
The arguments can be as follows:
-c <number> count pings to send
-d debug
-f ping flood
-i <number> wait number of seconds between each ping
-l <number> preload number of pings
-n numeric IP's only
-p pattern (in hex) to send as pad code in the ping header
-q quiet
-R record route
-s <number> packet size in bytes
-v Verbose output
So say that you wanna send 5 pings that's 128 bytes each to
IP 127.0.0.1, then you would do: ping -s 128 -c 5 127.0.0.1
-------------------------------------------------------------------------------
pmake
pmake is *BSD make (so I'm told), see make and: man pmake
-------------------------------------------------------------------------------
pnpdump
pnpdump gives a dump of all ISA pnp devices, good to use
with isapnp etc.
This is the command you wanna have a look at if your either
looking for exact info of some ISA device that is pnp, or
if your system has problems finding a ISA pnp device.
See the manual pages.
-------------------------------------------------------------------------------
portmap
portmap is the server that maps all RPC services, so if you
wanna use any RPC service you wanna have portmap running.
For more info: man portmap
-------------------------------------------------------------------------------
ps
ps gives you the process list, as in showing you the running
processes with there pid and other info.
do: ps --help
or: man ps for more info on what arguments it can be executed
with, personally I use: `ps aux` and `ps x` the most.
-------------------------------------------------------------------------------
pstree
process tree, a bit more (ascii) graphical version of ps,
do: pstree --help
or: man pstree
for more help on the arguments, personally I use it alone without
arguments.
-------------------------------------------------------------------------------
pwd
print working directory, shows you your current directory.
This command can be useful for 2 things what I know of,
one is to show you where you are, and the other in scripts
to do say: echo "output will go to: `pwd`/logfile"
-------------------------------------------------------------------------------
quota
quota prints the users quota, it works like
this: quota [arguments] <user/group>
Where the arguments can be:
-g Print group quotas for the group of which the user
is a member. The optional
-u flag is equivalent to the default.
-v will display quotas on filesystems where no storage
is allocated.
-q Print a more terse message, containing only infor-
mation on filesystems where usage is over quota.
For more info on the quota command do: man quota
-------------------------------------------------------------------------------
quotaoff
quotaoff turns the quota off for a file system.
quotaoff works like this: quotaoff [arguments] <filesystem>
The arguments can be as follows:
-a Force all file systems in /etc/fstab to have their
quotas disabled.
-v Display a message for each file system affected.
-u Manipulate user quotas. This is the default.
-g Manipulate group quotas.
This command is close to quotaon.
For more info: man quotaon
(Don't think there is a quotaoff man page, quotaon and quotaoff
seems to have the same manual page)
-------------------------------------------------------------------------------
quotaon
quotaon turns the quota on for a file system.
quotaon works like this: quotaon [arguments] <filesystem>
The arguments can be as follows:
-a All file systems in /etc/fstab marked read-write
with quotas will have their quotas turned on. This
is normally used at boot time to enable quotas.
-v Display a message for each file system where quotas
are turned on.
-u Manipulate user quotas. This is the default.
-g Manipulate group quotas.
For more info: man quotaon
-------------------------------------------------------------------------------
quotastats
quotastats displays the quota stats .... cant find any help, --help
or manual page for it.
-------------------------------------------------------------------------------
read
read, reads a variable.
Example:
echo -n "password: "
read pass
echo "Password was: $pass"
For more info: help read
-------------------------------------------------------------------------------
reboot
reboot does what it says, it reboots the system, you have to be root
to use this command.
reboot works the same as: shutdown -r now
or also the same as if you press: Ctrl+Alt+Del
Nothing much more to say about the reboot command.
-------------------------------------------------------------------------------
reset
reset resets the console, say that you have accidently done
cat <binary-file> so you totally screwed up your console
and you cant read anything on it, then just type `reset`
and press enter, and it should be back to normal within some seconds.
-------------------------------------------------------------------------------
rlogin
remote login, if you wanna use this command do: man rlogin
bore using it.
The most common use of it is: rlogin -l <username> <host>
-------------------------------------------------------------------------------
rm
remove, remove/unlink files, rm can be used with the
following arguments:
-d, --directory unlink directory, even if non-empty
(super-user only)
-f, --force ignore nonexistent files, never prompt
-i, --interactive prompt before any removal
-r, -R, --recursive remove the contents of directories recursively
-v, --verbose explain what is being done
--help display this help and exit
--version output version information and exit
An example is, that if you have a directory called /foo
that you wanna delete recursively, then you do: rm -rf /foo
Or say that you have a file /foo/bar that you wanna remove
without being prompted, then you do it like this: rm -f /foo/bar
-------------------------------------------------------------------------------
rmmod
remove modules, remove a loaded module.
List the modules that you can remove with lsmod.
And load modules with insmod.
man any of them for more information.
-------------------------------------------------------------------------------
route
route, displays the routing table by default.
The most common way of adding a route is like this:
route add -host <ip> gw <other-ip>
And to remove a post:
route del -host <ip> gw <other-ip>
An example would be, say that you want to route IP 123.123.123.123
to 127.0.0.1, this would drop any connection attempts from
123.123.123.123 to 127.0.0.1 so he cant connect to you or scan you,
(this is true in most cases), you would do:
route add -host 123.123.123.123 gw 127.0.0.1
Now the route command is bigger then that, so if you wanna
learn more about it do: man route
-------------------------------------------------------------------------------
rpm
rpm is a command that is is very important to most distributions.
rpm is short for 'redhat package manager' and was developed for
RedHat by Caldera.
rpm is a HUGE command, and works like this: rpm [arguments] <file>
but here are the most commonly used arguments:
rpm -ivh <package.rpm> installs package.rpm
rpm -Uvh <package.rpm> updates package.rpm
rpm -e <package> un-installed/erases package
rpm -qf <file> displays what package the file came with
rpm -qlp <package.rpm> displays the contents of the package.rpm
rpm -qRp <package.rpm> displays the dependencys needed by package.rpm
Other arguments and that are commonly used but not recommended are:
--force force install something
--nodeps do not check dependences
Another thing is if you installed a *.src.rpm file (that ends up in
/usr/src/RPM/*), you can compile a binary .rpm from it.
Say that you installed some-package.src.rpm, then you would go to:
/usr/src/RPM/SPECS/, and there type: rpm -ba some-package.spec
wait a while during the compile, and then you would have a
/usr/src/RPM/RPMS/<platform>/some-package.<platform>.rpm
the "<platform>" is your platform, as i386, i486, i586, i686,
k6, ppc, sprac, noarch etc.
To create an rpm from a .src.rpm you first need to know that
this should not be done as root for the simple reason that
if you make an rpm as root several unworking parts of it may
remain in your system generating errors if the compile of
the rpm isnt successful.
So the first thing you do to do this as user is to create a file
named .rpmmacros
And in that add the following:
%_topdir ~/RPM
This should work to create the file:
echo "%_topdir $HOME/RPM" > ~/.rpmmacros
Then you do this:
mkdir -p ~/RPM/{SOURCES,SPECS,BUILD,RPMS,SRPMS}
Now you're ready to start to build an rpm from a .src.rpm
first (as user, not as root) install the source rpm.
rpm -ivh package.src.rpm
Then you go to ~/RPM/SPECS/
The .src.rpm should have installed the sources in ~/RPM/SOURCES
and the spec file in ~/RPM/SPECS/
The spec file is like a script file, it tells rpm how to compile
the source and build the rpm.
Now find the spec file in ~/RPM/SPECS/, it's usually named the same
as the package, like this:
package.spec
So not to make an rpm out of it, do this:
rpm -ba package.spec
If this is successful (which it sadly enough isnt every time because
of ill written spec files)
You should now have an rpm file in ~/RPM/RPMS/<your architecture>
If you have a Pentium 2, the arch command will show "i586" and
so the rpm will be found in ~/RPM/RPMS/i586/
You will also have a brand new .src.rpm in ~/RPM/SRPMS/
If you need to do the rpm to any other target then your own
architecture, say you want to do it for i386, then you may do:
rpm -ba package.spec --target=i386
And so the new rpm will be found in ~/RPM/RPMS/i386/
This is about all there is to say about the rpm command in this
tutorial.
The rpm command and the spec file *scripting* langauge
would need a rather large tutorial by it self to be explained
in full .... so I wont take up all that here.
For more info on the rpm command do: man rpm
-------------------------------------------------------------------------------
sed
sed, stream editor, is already breafly explained in this tutorial,
so if you want more info do: man sed
-------------------------------------------------------------------------------
setleds
setleds may show or set the flags and lights on NumLock, CapsLock
and ScrollLock.
On it's own without any arguments it shows the current settings.
The syntax is this: setleds [arguments] <+/-num,caps,scroll>
Here's the arguments:
-F This is the default. Only change the VT flags (and
their setting may be reflected by the keyboard
leds).
-D Change both the VT flags and their default settings
(so that a subsequent reset will not undo the
change). This might be useful for people who always
want to have numlock set.
-L Do not touch the VT flags, but only change the
leds. From this moment on, the leds will no longer
reflect the VT flags (but display whatever is put
into them). The command setleds -L (without further
arguments) will restore the situation in which the
leds reflect the VT flags.
-num +num
Clear or set NumLock. (At present, the NumLock
setting influences the interpretation of keypad
keys. Pressing the NumLock key complements the
NumLock setting.)
-caps +caps
Clear or set CapsLock. (At present, the CapsLock
setting complements the Shift key when applied to
letters. Pressing the CapsLock key complements the
CapsLock setting.)
-scroll +scroll
Clear or set ScrollLock. (At present, pressing the
ScrollLock key (or ^S/^Q) stops/starts console out-
put.)
Here is a few example, where the first one is from the manualpage,
(I'd hate to break the cut'n'paste tradition from the manual pages
now), so here are some examples:
INITTY=/dev/tty[1-8]
for tty in $INITTY; do
setleds -D +num < $tty
done
This would set numlock on for tty1 to tty8
Here's another short example:
while /bin/true; do
setleds -L +caps; usleep 500000
setleds -L +num; usleep 500000
setleds -L -caps; usleep 500000
setleds -L -num; usleep 500000
done
This would flash the NumLock and CapsLock leds, for infinety.
For more info do: man setleds
-------------------------------------------------------------------------------
seq
sequence numbers.
seq works baskically like this:
seq [OPTION] LAST
seq [OPTION] FIRST LAST
seq [OPTION] FIRST INCREMENT LAST
And can be used with the following options:
-f, --format FORMAT use printf(3) style FORMAT (default: %g)
-s, --separator STRING use STRING to separate numbers (default: n)
-w, --equal-width equalize width by padding with leading zeroes
--help display this help and exit
--version output version information and exit
Here's some small examples and what they do:
seq 10 (Count from 1 to 10)
seq 5 10 (Count from 5 to 10)
seq 1 2 10 (Count from 1 to 10 by incrementing two: 1,3,5,7,9)
seq 10 0 (Count backwards from 10 to 0)
For more info do: seq --help
-------------------------------------------------------------------------------
sleep
sleep works like this: sleep <number of seconds>
Not much to say about this command, ... if you wanna read
more about it: man sleep
-------------------------------------------------------------------------------
sort
sort, sorts the contents of a file and gives the output to stdout.
By default it sorts it in alphabetical order, sort works
like this: sort [arguments] <file>
sort can be executed with the following arguments:
-b ignore leading blanks in sort fields or keys
-c check if given files already sorted, do not sort
-d consider only [a-zA-Z0-9 ] characters in keys
-f fold lower case to upper case characters in keys
-g compare according to general numerical value, imply -b
-i consider only [ 40- 176] characters in keys
-k POS1[,POS2]
start a key at POS1, end it *at* POS2
field numbers and character offsets are numbered
starting with one (contrast with zero-based +POS form)
-m merge already sorted files, do not sort
-M compare (unknown) < `JAN' < ... < `DEC', imply -b
-n compare according to string numerical value, imply -b
-o FILE
write result on FILE instead of standard output
-r reverse the result of comparisons
-s stabilize sort by disabling last resort comparison
-t SEP use SEParator instead of non- to whitespace transition
-T DIRECTORY
use DIRECTORY for temporary files, not $TMPDIR or /tmp
-u with -c, check for strict ordering; with -m, only
output the first of an equal sequence
-z end lines with 0 byte, not newline, for find -print0
--help display the help and exit
--version output version information and exit
One more time I give thanks to the cut & paste function.
Here's an example of sort: sort file1 -o sorted-file2
This command works good with the `uniq` command to sort out
duplica words, like this: sort file1 | uniq > sorted-file
For more info do: man sort
-------------------------------------------------------------------------------
ssh
secure shell, works a bit like telnet but has encryption,
ssh is becoming a good standard of encrypted remote shell connections.
ssh is however not usually default included in any distros,
and there is several versions of it, so if you download it
make sure to read all documentations about it.
Even though it's not default included, I still wanned to include it
in this tutorial to make users that use LAN connections
as local networks with more then one user or cable modems aware
of this tool, because if they use telnet anyone on the local
subnet can sniff the connection and get any login and password
used with incoming or outgoing telnet connections.
Really anyone can sniff anything that's not encrypted, like
ftp logins and passwords, http, IRC, and everything like that.
but the most vital to protect is the ways people can enter
your system, so if you are on a LAN with more then one user
or have any form of cable or non-dialup connection,
then disable telnet (put a # in front of the telnet line in
/etc/initd.conf and after that do: killall -HUP initd), and then
install ssh.
-------------------------------------------------------------------------------
strip
strip strips binary files (executables) of junk code,
such as debugging information.
This may be very useful to bring down the size of executable files.
BUT beware, if you strip the kernel or any other very complex
binary, they are likely to malfunction, so use this command
wisely, and read it's manual page.
-------------------------------------------------------------------------------
su
su, the manual pages says substitute user and the UNIX command bible
says super user ... so it means any of those, it's however used
to *become another user*, if you are root and su <user> you wont
need to supply any password.
If you type only `su` as user you will become root if you have the
aproperiet root password.
su can be used with the following arguments:
-, -l, --login make the shell a login shell
-c, --commmand=COMMAND pass a single COMMAND to the shell with -c
-f, --fast pass -f to the shell (for csh or tcsh)
-m, --preserve-environment do not reset environment variables
-p same as -m
-s, --shell=SHELL run SHELL if /etc/shells allows it
--help display this help and exit
--version output version information and exit
Say now that you wanna su to root and have root's path/enviorment.
then you do: su -
Or say that you wanna execute a single command as root from being
a user, say the command `adduser`, then you do: su -c "adduser"
you will be prompted for the password, and if you can supply it
the command will be executed as root.
-------------------------------------------------------------------------------
swapoff
turns swap off, it can be used with the following arguments:
-h Provide help
-V Display version
-s Display swap usage summary by device. This option
is only available if /proc/swaps exists (probably
not before kernel 2.1.25).
-a All devices marked as ``sw'' swap devices in
/etc/fstab are made available.
-p priority (man swapon and swapoff for more info on prioretys)
Example, say that you wanna turn all swap partitions (from /etc/fstab)
off then you do: swapoff -a
Again, for more info: man swapoff
-------------------------------------------------------------------------------
swapon
swapon is the opposite of swapoff but has the same arguments.
See: man swapon
-------------------------------------------------------------------------------
tail
tail gives by default the last 10 lines out of a file, it's very alike
the `head` command, ad works like this: tail [arguments] <file>
The most common usage of tail is this:
tail -f <file> This will append the data to stdout as the file grows.
very good to view logs as they come in.
tail -50 <file> Displays the last 50 lines from a file.
tail has more arguments which you can learn in it's manual page
if you are interested, do: man tail
-------------------------------------------------------------------------------
talk
talk is a little daemon controlled by inetd, so if it doesn't
work on your local machine make sure the talk line in
/etc/inetd.cond are not remmed by a leading # character.
Talk gives a real time text chat, in a horizontally divided
window or rather console.
Talk works like this: talk user@host
or just user if it's on the local machine.
Say that I wanna send a talk request to user `alfa` on IP
123.123.123.132, and I'm user `beta` on 234.234.234.234.
Then I type: talk alfa@123.123.123.132
And he as answer when the request comes
types: talk beta@234.234.234.234
What to type as answer comes up when you get a talk request.
For more info on the talk command do: man talk
-------------------------------------------------------------------------------
tar
tar, UNIX tape archive, is yet another huge command,
it's used to compress a directory to a compressed .tar file,
or a single file to a tar file.
tar works like this: tar [arguments] <directory-or-file>
Here are the most common examples of tar usage:
tar -zvxf <file.tar.gz> uncompress a .tar.gz or .tgz archive
tar -vxf <file.tar> uncompress a .tar archive
tar -c --file=<file.tar> <directory> crates a .tar archive
tar -cf <file.tar> <directory> - same as above -
tar -tf <file.tar> list the contents of a .tar file
tar -tzf <file.tar.gz> list the contents of a .tar.gz or a .tgz file
tar -czvf <file.tar.gz> <directory> crates a .tar.gz archive
For more info on the tar command, do: man tar
-------------------------------------------------------------------------------
tcpdump
tcpdump is a command that let's you view the traffic on the local
subnet or segment, It's not default on many Linux distributions.
So if you have it or get it, read it's documentation and it's
manual pages, if you want to use it.
-------------------------------------------------------------------------------
telnet
telnet is the most basic of all clients to know.
It's not often you will ever use it in other ways
then: telnet <host-or-ip> <port>
And it's not even so often one uses it with the port number after.
Telnet creates a real time connection to another computer,
ofcorse the other computer needs a running telnet daemon,
and you need to have a login and a password to get in.
But when you get in you can remotely work on the other system
just as if you sat in front of it.
Times when it's good to supply a port number after the host is
most commonly to check the version of some daemon/server,
as if you want to know the version of your own sendmail, you
can always do: telnet 127.0.0.1 25
smtp (send mail transfer protocol) runs on port 25.
If you wonder what port something runs on check in /etc/services
For more info on telnet do: man telnet
-------------------------------------------------------------------------------
test
test is a big command, and is used to generate boolean results
out of 2 arguments, to explain the whole command here would take up
to much space and time, it can be used like this:
test -f /sbin/shutdown && echo "It's there" || echo "It's not there"
That line says in clear english:
test if file /sbin/shutdown is there, if outcome is true
echo "It's there" else echo "It's not there".
You can test if a file is executeble, if a string is non-zero etc.
Just about anything you can think of.
For more info on the many things you can do with the `test`
command, do: man test
-------------------------------------------------------------------------------
touch
touch will by default change the date on a file to the current date.
It works like this: touch [arguments] <file>
If the file doesn't exist if will create a file that's 0 bytes big.
The following arguments can be used with touch:
-a change only the access time
-c do not create any files
-d, --date=STRING
parse STRING and use it instead of current time
-f (ignored)
-m change only the modification time
-r, --reference=FILE
use this file's times instead of current time
-t STAMP
use [[CC]YY]MMDDhhmm[.ss] instead of current time
--time=WORD
access -a, atime -a, mtime -m, modify -m, use -a
--help
display the help and exit
--version
output version information and exit
So say that you have a file called 'file' that I want to change date of
to say 'Aug 21 1999 04:04',
then you would do: touch -t 9908210404 file
For more info on this command do: man touch
-------------------------------------------------------------------------------
tr
translate characters, this command can change all upper case
characters to lower case characters in a file or substitute
all mumbers to some other characters etc.
tr's syntax is: tr [arguments] <SET1> <SET2>
tr can be used with the following arguments:
-c, --complement
first complement SET1
-d, --delete
delete characters in SET1, do not translate
-s, --squeeze-repeats
replace sequence of characters with one
-t, --truncate-set1
first truncate SET1 to length of SET2
--help
display this help and exit
--version
output version information and exit
And the SET's are as follows:
[:alnum:]
all letters and digits
[:alpha:]
all letters
[:blank:]
all horizontal whitespace
[:cntrl:]
all control characters
[:digit:]
all digits
[:graph:]
all printable characters, not including space
[:lower:]
all lower case letters
[:print:]
all printable characters, including space
[:punct:]
all punctuation characters
[:space:]
all horizontal or vertical whitespace
[:upper:]
all upper case letters
[:xdigit:]
all hexadecimal digits
[=CHAR=]
all characters which are equivalent to CHAR
Examples of tr is:
cat file | tr [:upper:] [:lower:] (change all uppercase to lower)
cat file | tr -d [:alnum:] (delete all numbers and chars)
For more info on tr, do: man tr
-------------------------------------------------------------------------------
traceroute
traceroute is a command that traces a route to an IP/host
and will give you the number of hops from your computer
to the remote computer, and will display the ping times
to each computer in the way.
traceroute has some arguments that I never needed to use
but if you feel curious about this command, feel free
to look at the manual pages for it: man traceroute
-------------------------------------------------------------------------------
ulimit
ulimit sets a limit for how much memory etc. users are allowed
to use.
It works like this: ulimit [arguments]
And the arguments can be the following:
-S use the `soft' resource limit
-H use the `hard' resource limit
-a show all settings
-c core file size (in blocks)
-d data seg size (in kilo bytes)
-f file size (in blocks)
-l max locked memory (in kilo bytes)
-m max memory size (in kilo bytes)
-n open files (number)
-p pipe size (512 bytes)
-s stack size (in kilo bytes)
-t cpu time (in seconds)
-u max user processes (number)
-v virtual memory (kilo bytes)
Say that I want to set a limit that users can only run 50
processes each, the I would do: ulimit -u 50
-------------------------------------------------------------------------------
umount
un mount, un mounts a mountpoint, say that you have mounted your
CD-rom drive on /mnt/cdrom then you would do: umount /mnt/cdrom
to unmount it.
I never used any arguments to this command, but if you wanna learn
about them, feel free to do: man umount
-------------------------------------------------------------------------------
unalias
unalias removes a defined alias, say that you have an alias
like this: alias du='du -h'
And you want to remove it: then you simply do: unalias du
To remove all aliases do: unalias -a
For more info do: help unalias
-------------------------------------------------------------------------------
uname
uname gives info on the current system, and works as
this: uname [arguments]
The arguments can be the following:
-a, --all print all information
-m, --machine print the machine (hardware) type
-n, --nodename print the machine's network node hostname
-r, --release print the operating system release
-s, --sysname print the operating system name
-p, --processor print the host processor type
-v print the operating system version
--help display this help and exit
--version output version information and exit
The most common way of using uname is: uname -a
-------------------------------------------------------------------------------
uncompress
uncompress uncompresses .Z files, for more info do: man uncompress
-------------------------------------------------------------------------------
uniq
uniq does by default take away duplica words out of a text,
which can be good if your sorting out a dictionary.
But `uniq` can also be executed with the following arguments:
-c, --count
prefix lines by the number of occurrences
-d, --repeated
only print duplicate lines
-D, --all-repeated
print all duplicate lines
-f, --skip-fields=N
avoid comparing the first N fields
-i, --ignore-case
ignore differences in case when comparing
-s, --skip-chars=N
avoid comparing the first N characters
-u, --unique
only print unique lines
-w, --check-chars=N
compare no more than N characters in lines
-N same as -f N
+N same as -s N
--help
display the help and exit
--version
output version information and exit
For more info on this command do: man uniq
-------------------------------------------------------------------------------
unset
this command will remove an alias or function.
It has the following options:
-v unset a variable only.
-f unset a function only.
By default unset will first try to unset as a variable and if that
fails it will try to unset as a function.
Here's an example:
alien:~$ foo=bar
alien:~$ echo $foo
bar
alien:~$ unset foo
alien:~$ echo $foo
alien:~$
For more info, do: help unset
-------------------------------------------------------------------------------
unzip
unzip is the tool or command to unzip files, it works like this:
unzip [arguments] <file.zip>
unzip has some arguments I never used, do: unzip --help
to get a list of valid arguments.
Also feel free to do: man unzip
-------------------------------------------------------------------------------
updatedb
update the locate database, updatedb works like this:
updatedb [arguments] <pattern>
By default updatedb updates the locate database so it covers the
whole system and all it's files, but has the following arguments:
-u Create slocate database starting at the root direc-
tory. This is the default behavior when called as updatedb.
-U path
Create slocate database starting at path path.
-e dirs
Exclude directories in the comma-separated list
dirs from the slocate database.
-f fstypes
Exclude file systems in the comma-separated list
dirs from the slocate database.
-l <num>
Security level. -l 0 turns security checks off,
which will make searches faster. -l 1 turns security
checks on. This is the default.
-q Quiet mode; error messages are suppressed.
-v Verbose mode; display files indexed when creating database
--help
Print a summary of the options to slocate and exit.
--version
Print the version number of slocate and exit.
If you have the whole system updataded in the locate databse,
to find a file all you have to do is to: locate <file>
For more info: man updatedb
-------------------------------------------------------------------------------
uptime
displays the current uptime (the time the system has been on).
with the load average.
It shows from left to right:
The current time, how long the system has been running,
how many users are currently logged on, and the system load
averages for the past 1, 5, and 15 minutes.
Also do: man uptime
-------------------------------------------------------------------------------
useradd
useradd adds a user account to the system.
useradd works like this: useradd [arguments] user
Here's a cut & paste from it's manual page (as usual).
-c comment
The new user's password file comment field.
-d home_dir
The new user will be created using home_dir as the
value for the user's login directory. The default
is to append the login name to default_home and use
that as the login directory name.
-e expire_date
The date on which the user account will be dis-
abled. The date is specified in the format YYYY-
MM-DD.
-f inactive_days
The number of days after a password expires until
the account is permanently disabled. A value of 0
disables the account as soon as the password has
expired, and a value of -1 disables the feature.
The default value is -1.
-g initial_group
The group name or number of the user's initial
login group. The group name must exist. A group
number must refer to an already existing group.
The default group number is 1.
-G group,[...]
A list of supplementary groups which the user is
also a member of. Each group is separated from the
next by a comma, with no intervening whitespace.
The groups are subject to the same restrictions as
the group given with the -g option. The default is
for the user to belong only to the initial group.
-m The user's home directory will be created if it
does not exist. The files contained in skele-
ton_dir will be copied to the home directory if the
-k option is used, otherwise the files contained in
/etc/skel will be used instead. Any directories
contained in skeleton_dir or /etc/skel will be cre-
ated in the user's home directory as well. The -k
option is only valid in conjunction with the -m
option. The default is to not create the directory
and to not copy any files.
-M The user home directory will not be created, even
if the system wide settings from /etc/login.defs is
to create home dirs.
-n A group having the same name as the user being
added to the system will be created by default.
This option will turn off this Red Hat Linux spe-
cific behavior.
-r This flag is used to create a system account. That
is, an user with an UID lower than value of UID_MIN
defined in /etc/login.defs. Note that useradd will
not create a home directory for such an user,
regardless of the default setting in
/etc/login.defs. You have to specify -m option if
you want a home directory for a system account to
be created. This is an option added by Red Hat.
-p passwd
The encrypted password, as returned by crypt(3).
The default is to disable the account.
-s shell
The name of the user's login shell. The default is
to leave this field blank, which causes the system
to select the default login shell.
-u uid The numerical value of the user's ID. This value
must be unique, unless the -o option is used. The
value must be non-negative. The default is to use
the smallest ID value greater than 99 and greater
than every other user. Values between 0 and 99 are
typically reserved for system accounts.
When the -D argument is used useradd with either give the
default values or update them if there is more arguments.
The other arguments can be:
-b default_home
The initial path prefix for a new user's home
directory. The user's name will be affixed to the
end of default_home to create the new directory
name if the -d option is not used when creating a
new account.
-e default_expire_date
The date on which the user account is disabled.
-f default_inactive
The number of days after a password has expired
before the account will be disabled.
-g default_group
The group name or ID for a new user's initial
group. The named group must exist, and a numerical
group ID must have an existing entry .
-s default_shell
The name of the new user's login shell. The named
program will be used for all future new user
accounts.
Also feel free to read the manual page: man useradd
-------------------------------------------------------------------------------
userdel
userdel removes a user from the system.
userdel works like this: userdel [argument] <user>
The only argument to this command is:
-r removes the users home directory, along with the user.
This will delete the users login and everything from the system.
userdel will not remove the user if he is currently logged
in to the system or have any processes running.
So make sure you kill all processes owned by the user,
if any, before removing his/her account.
To kill the all running processes owned by the same user
you can do the following command (change <user> to the username):
for pids in `ps U <user> | cut -c 1-6`; do kill -9 $pids ; done
-------------------------------------------------------------------------------
users
Display the currently logged in users.
-------------------------------------------------------------------------------
usleep
usleep is another version of the sleep command, but instead of beeing
told how many seconds to sleep, it sleeps in microseconds.
So `usleep 1000000` makes it sleep for 1 second.
-------------------------------------------------------------------------------
w
w is like a mix of who and finger, it's used to see who's logged
on to the system and will show the following:
login name, terminal, host, login time, idle time, JCPU (total cpu time
that user (terminal) takes up), PCPU (cpu time of the users current
process which is shown in the next field), what (process)
-------------------------------------------------------------------------------
wall
wall is a superuser command to send a string of text to all
consoles/terminals, wall can work either like: wall <string>
or: wall <file with string in it>
To wall special characters like "=)" you need to do it like
this: wall '<string> =)'
-------------------------------------------------------------------------------
wc
word count, works basicly like this: wc [argument] <file>
Where the arguments can be any of the following:
-c, --bytes, --chars print the byte counts
-l, --lines print the newline counts
-L, --max-line-length print the length of the longest line
-w, --words print the word counts
--help display this help and exit
--version output version information and exit
So to find out the number of words in a file called say "file1",
you would do: wc -w file1
Or to find out the number of lines in the same file you would
do: wc -l file1
This little tool can prove to be very useful, though when you
use it with the -l/--lines argument it will only count lines that
contains any characters, if you wanna count all lines
including empty lines, use: grep -c . file1
or the same thing in another way: cat file1 | grep -c .
-------------------------------------------------------------------------------
whatis
whatis searches for words in the whatis database, say that you
are looking for a manual page about the `shutdown` command.
Then you can do: whatis shutdown
for more information, do: man whatis
Or: man apropos
-------------------------------------------------------------------------------
whereis
whereis looks for something just as the `which` command here below.
but looks for matches in more places, as the manual page directory's.
It works like this: whereis [argument] <what-you-wanna-find>
Try this command a few times, and if you want to learn
more about it as it's arguments and so do: man whereis
-------------------------------------------------------------------------------
which
which will tell you where a command is located, as if you
do: which shutdown
it will answer: /sbin/shutdown
This command will search your path for whatever you type after it.
This command is best used in scripts and functions, like this:
function whichrpm { rpm -qf `which $1`; }
The which command has some arguments, and more examples in it's
manual page, so for more info do: man which
-------------------------------------------------------------------------------
who
who is a little command that shows you who's logged on,
on what tty and at what time they logged on.
I never ever used this command with any arguments,
but if you want to learn more about this command do: who --help
or: man who
-------------------------------------------------------------------------------
whoami
displays your user name, same as `id -un`.
whoami can be used with the following arguments:
--help display this help and exit
--version output version information and exit
Not much more to say about this command.
-------------------------------------------------------------------------------
whois
whois is a tool that asks internic for information on a domain name.
This is only for .com .org .net etc.
If any luck it will give you the name and other info of the one that
registered the domain, and it's name servers.
whois can also be used to do: whois user@host
For more info on this command do: man whois
Or: man fwhois
-------------------------------------------------------------------------------
yes
yes is a command that repeats the same thing over and over again,
it's used as this: yes <string>
If no string or word is supplied it will repeat the character 'y'.
yes can be used with the following arguments:
--version display the version and exit.
--help display the help and exit.
-------------------------------------------------------------------------------
zip
zip is a compression tool, to compress with zip do:
zip [arguments] <file.zip> <file1> <file2> etc.
The arguments can be the following:
-f freshen: only changed files
-u update: only changed or new files
-d delete entries in zipfile
-m move into zipfile (delete files)
-r recurse into directories
-j junk (don't record) directory names
-0 store only
-l convert LF to CR LF (-ll CR LF to LF)
-1 compress faster
-9 compress better
-q quiet operation
-v verbose operation/print version info
-c add one-line comments
-z add zipfile comment
-@ read names from stdin
-o make zipfile as old as latest entry
-x exclude the following names
-i include only the following names
-F fix zipfile (-FF try harder)
-D do not add directory entries
-A adjust self-extracting exe
-J junk zipfile prefix (unzipsfx)
-T test zipfile integrity
-X eXclude eXtra file attributes
-y store symbolic links as the link instead of the referenced file
-R PKZIP recursion (see manual)
-h show the help
-n don't compress these suffixes
To uncompress a zip file, use the `unzip` command.
-------------------------------------------------------------------------------
And that is most of the commands you'll ever encounter while scripting or
using a *nix system.
There are LOADS of other commands, but not many that are as used as these
I just explained.
There are more really useful commands that I never seen as default
on any system aswell, like pgp and gpg, I havent included those since
there full documentation comes with the same package as that
command/application if you download it.
So, as I said these are the most useful commands, but if someone out there
think I missed some really useful command send me a mail and I'll add it.
Posted in