Linux Guide/Linux commands

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=master T.A@gmail.com Adams

An A-Z Index of the Linux BASH command line

Note: The majority of commands listed here belong to coreutils.

Command Description
alias Create an alias
apropos Search manual for keyword
at Schedule a job to run in the future.
awk Find and Replace text within file(s)
break Exit from a loop
builtin Run a shell builtin
bunzip2 Decompress file from bzip2 format
bzip2 Compress file to bzip2 format
cal Display a calendar
case Conditionally perform a command
cat Concatenate files to standard output
cd Change Directory
cfdisk Partition table manipulator for Linux
chgrp Change group ownership
chmod Change access permissions
chown Change file owner and group
chroot Run a command with a different root directory
chvt Change the virtual Terminal
cksum Print CRC checksum and byte counts
clear Clear terminal screen
cmp Compare two files
comm Compare two sorted files line by line
command Run a command - ignoring shell functions
compress Compress file(s) to old Unix compress format
continue Resume the next iteration of a loop
convmv A perl script that converts filenames from one encoding to another
cp Copy one or more files to another location
cron Daemon to execute scheduled commands at predefined time
crontab Schedule a command to run at a later time
csplit Split a file into context-determined pieces
cut Divide a file into several parts
date Display or change the date & time
dc Desk Calculator
dd Data Dump - Convert and copy a file
declare Declare variables and give them attributes
df Display free disk space
diff Display the differences between two files
diff3 Show differences among three files
dir Briefly list directory contents
dircolors Colour setup for `ls'
dirname Convert a full pathname to just a path
dirs Display list of remembered directories
du Estimate file space usage
echo Display message on screen
ed A line-oriented text editor
egrep Search file(s) for lines that match an extended expression
eject Eject CD-ROM
enable Enable and disable builtin shell commands
env Disp, set, or remove environment variables
eval Evaluate several commands/arguments
exec Execute a command
exit Exit the shell
expand Convert tabs to spaces
export Set an environment variable
expr Evaluate expressions
factor Print prime factors
false Do nothing, unsuccessfully
fdformat Low-level format a floppy disk
fdisk Partition table manipulator for Linux
fgrep Search file(s) for lines that match a fixed string
file Determine type of file
find Search for files that meet a desired criteria
fmt Reformat paragraph text
fold Wrap text to fit a specified width.
for Expand words, and execute commands
format Format disks or tapes
free Disp, s memory usage
fsck Filesystem consistency check and repair.
fstat List open files
function Define Function Macros
fuser Identify process using file
gawk Find and Replace text within file(s)
getopts Parse positional parameters
grep Search file(s) for lines that match a given pattern
groups Print group names a user is in
gunzip Decompress file(s) from GNU zip format
gzcat Show contents of compressed file(s)
gzip Compress file(s) to GNU zip format
hash Remember the full pathname of a name argument
head Output the first part of file(s)
history Command History
hostname Print or set system name
iconv Converts the encoding of characters from one code page encoding scheme to another.
id Print user and group id's
if Conditionally perform a command
import Capture an X server screen and save the image to file
info Help info
install Copy files and set attributes
join Join lines on a common field
kill Stop a process from running
less Display output one screen at a time
let Perform arithmetic on shell variables
ln Make links between files
local Create variables
locate Find files
logname Print current login name
logout Exit a login shell
lpc Line printer control program
lpr Off line print
lprint Print a file
lprintd Abort a print job
lprintq List the print queue
lprm Remove jobs from the print queue
ls List information about file(s)
ll #ls -l List information about file(s)
lsof List open files
m4 Macro processor
makewhatis Rebuild whatis database
man Print manual pages
mkdir Create new folder(s)
mkfifo Make FIFOs (named pipes)
mknod Make block or character special files
more Display output one screen at a time
mount Mount a file system
mtools Manipulate MS-DOS files
mv Move or rename files or directories
netconfig Configure your network
nice Set the priority of a command or job
nl Number lines and write files
nohup Run a command immune to hangup
od View binary files
passwd Modify a user password
paste Merge lines of files
pathchk Check file name portability
popd Restore the previous value of the current directory
pr Convert text files for printing
printcap Printer capability database
printenv Print environment variables
printf Format and print data
ps Process status
pushd Save and then change the current directory
pwd Print Working Directory
quota Display disk usage and limits
quotacheck Scan a file system for disk usage
quotactl Set disk quotas
pax Archive file(s)
ram ram disk device
rcp Copy files between two machines.
read read a line from standard input
readonly Mark variables/functions as readonly
remsync Synchronize remote files via email
return Exit a shell function
rm Remove (delete) files
rmdir Remove folder(s)
rpm RPM Package Manager (was RedHat Package Manager)
rsync Remote file copy (Synchronize file trees)
screen Terminal window manager
sdiff Merge two files interactively
sed Stream Editor
select Accept keyboard input
seq Print numeric sequences
set Manipulate shell variables and functions
shift Shift positional parameters
shopt Shell Options
shutdown Shutdown or restart linux
sleep Delay for a specified time
sort Sort text files
source Run commands from a file `.'
split Split a file into fixed-size pieces
strings print the strings of printable characters in (binary) files.
su Substitute user identity
sum Print a checksum for a file
symlink Make a new name for a file
sync Synchronize data on disk with memory
tac Print files out in reverse line order
tail Output the last part of files
tar Tape ARchiver
tee Redirect output to multiple files
test Evaluate a conditional expression
time Measure Program Resource Use
times User and system times
timidity Play midi files and set up software synth to play midi files with other commands.
touch Change file timestamps
top List processes running on the system
traceroute Trace Route to Host
trap Run a command when a signal is set(bourne)
tr Translate, squeeze, and/or delete characters
true Do nothing, successfully
tsort Topological sort
tty Print filename of terminal on stdin
type Describe a command
ulimit Limit user resources
umask Users file creation mask
umount Unmount a filesystem
unalias Remove an alias
uname Print system information
unexpand Convert spaces to tabs
uniq Uniquify files (remove all duplicate lines)
units Convert units from one scale to another
unset Remove variable or function names
unshar Unpack shell archive scripts
until Execute commands (until error)
useradd Create new user account
usermod Modify user account
users List users currently logged in
uuencode Encode a binary file into 7-bit ASCII characters
uudecode Decode a file created by uuencode
v Verbosely list directory contents (`ls -l -b')
vdir Verbosely list directory contents (`ls -l -b')
watch Execute/display a program periodically
whatis List manual pages by name
wc Print byte, word, and line counts of a file
whereis Report all known instances of a command
which Locate a program file in the user's path.
while Execute commands
who Print all usernames currently logged in
whoami Print the current user id and name (`id -un')
xargs Execute utility, passing constructed argument list(s)
yes Print a string until interrupted
zcat Show contents of compressed file(s)
zip Compress and archive file(s) to zip format
.period Run commands from a file
### Comment / Remark
The next list is from Transwiki:Useful unix command. Commands should be merged into the table above, with longer explanations placed somewhere in Guide to Unix/Commands. X11 commands go in the Guide to X11 book. Some of these are applications (like acroread); someone needs to find a book or place for them.

so that you can't recursively delete your /dev directory without telling the system you're sure you want to do it.

The syntax for the absolute version is

To set the uid to the owner's permissions, use

To set the uid to the group's permissions, use

There are lots of security issues related to allowing a program to have root's permissions when run by an ordinary user. I don't pretend to understand all of these issues.

To restore from diskettes, use:

The cpio command will prompt the user to insert more diskettes as they are needed. The command for mirroring a directory structure is the following:

This copies the working directory and its contents, including subdirectories, into /destinationdirectory. In order to copy an individual file which is larger than a floppy, use:

The ibs and bs options specify the block sizes for input and for both input and output. A boot disk image can be directly copied to a floppy using the second of the two dd commands above.

will display detailed disk usage for each subdirectory starting at root, giving files sizes in bytes.

where the filesystem is on /dev/devicename. The device should not be mounted, and this program must be run as root.

This is a shell builtin.

in order to find files matching a particular name on the working directory and all subdirectories. Find can be incredibly powerful, but it is incredibly obscure.

did work. The single quotes are necessary. The files necessary to run grub are normally located in /boot/grub. Once the file menu.lst has been edited and appropriated entries added to boot the different operating systems on one's hard disk(s), the following sequence of commands can be used to install grub in the master boot record (MBR) sector of the hard disk:

Here, the x should be replaced by the partition where the /boot/grub directory is located, which is probably the root partition of the Linux system. Note that grub has its own conventions for naming devices and numbering partitions, so that for example a partition which is called hda6 under Linux will be called (hd0,5) by grub.

The -C option to lilo has lilo use the lilo.flop file instead of the default lilo.conf.

To get this all the time, add

to .bashrc. The following command

will give directory listings in color, with file sizes in kilobytes, and append a character to the file to indicate its type.

The default device for execution of these commands is /dev/fd0 and can be referred to as ``a:''.

The user's home directory on the remote system must contain the file .rhosts with a list of users (preceded by the full domain name or exact IP address of their machine) with access privileges.

The remote computer must recognize the local user and the local machine. See the rcp command for how to set up the .rhosts file on the remote machine.

We need to find out about installing the rpm package on a Slackware box. It's probably better to use a package converter such as alien.

prints the current user environment, giving the values of currently defined variables.

The system subtracts x, y and z from the owner, group and other file permissions that it would otherwise assign to new files. This is a shell builtin.

See the man pages for X, xdm, and Xserver. As usual, the man pages are pretty obscure. The best single source seems to be the Xserver man pages. After X is configured, X needs to be started at bootup with the command (in /etc/rc.d/init.d/xterm):

If the address of a nameserver is not configured, then the numeric address of the remote machine rather than its name should be entered. If the machines are connected through ethernet cards and the net, then obviously basic networking has to be set up. Gnome and KDE come with their own versions of X display/login managers, called respectively gdm and kdm.

Then, log onto the remote machine using rlogin (see above) or telnet. Once logged in, use the following command to get the remote X server to open an X terminal on the local machine:

This is valid for csh, which is the default login shell on Nobel. For ksh, (and I think bash) replace with

Other X-based programs such as Netscape or Gauss (graphical version) can also be run on a remote machine with display on the local machine with little trouble. The local X server is the program that has all of the information concerning the properties of the graphics card and terminal, so it must be necessary to have X running on the local machine. The following should also work. After using xhost to give permission to the remote machine to display on the local machine, use

Question: can one start the X session on the local machine and then run a remote copy of a window manager?

into the .xession (with xdm) or the .xinitrc (with startx) file.

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