Linux Commands

UNIX Commands

Login and Exit
yppasswd Change password
rlogin machine Log into a remote machine
telnet machine Log into a remote machine
exit End a shell session
Ctrl-D End shell session
logout Log out of remote session

Help


man command Describes the command
man -k keyword Search for keyword

Display directory listing

ls Display directory listing
ls -l Display access permissions
ls -a Display hidden files
ls -d Display directory
ls -t Display files sorted by time
ls dir Display contents of directory
ls file Display file
ls ???* Display all files with more than 3 characters in name

Change, Create, Remove Directories

pwd Display current directory
cd Change to your home directory
cd .. Change to parent directory
cd dir Change to another directory
mkdir dir Create a new directory
rmdir dir Remove a directory (must be empty)
rm -r dir Remove a directory and everything within it

Create, Copy, Move, Delete Files

touch file Create an empty file
cp src-file dst-file Copy a file to another file
cp src-file dst-dir Copy a file to a directory
cp -r * dst-dir Copy all files and sub-directories to another directory
mv src-file dst-file Move a file to another file (renames file)
mv src-file dst-dir Move a file to another directory
mv src-dir dst-dir Move a directory to another directory
Note: filenames can be up to 255 characters long but should not contain special
characters, e.g., $ * [ ] & < >


Change file permissions

chmod o+r file Change file to allow read access to anyone
chown username file Change onwer of file to username
chgrp new-grp file Change group owner of file to new-grp
Note: -rwxr-x--- shows permissions on a regular file to be:
owner=read,write,execute; group=read,execute; others=nothing

Display Contents of a File

cat file Display contents of file
cat -v file Display non-printing characters
head file Display first 10 lines
tail file Display last 10 lines
more file Display file one screen at a time
wc file Count number of words in file
Sort, Compare, Convert, Compress Files
sort file1 > file2 Sort lines in file1 and output to file2
sort -1 -n file1 > file2 Sort by column 1 numerically and output to file2
uniq input-file Remove or report adjacent duplicate lines
unix2dos unx-file dos-file Convert from UNIX to DOS format
dos2unix dos-file unx-file Convert from DOS to UNIX format
cmp file1 file2 Compare byte-by-byte 2 files
diff file1 file2 Compare line by line 2 files
sdiff file1 file2 Compare 2 files by displaying them side by side
compress file Compress a file
gunzip file Uncompress a file
tar cf file.tar . Create a tar archive of current directory
tar xf file.tar Restore tar archive to current directory

Search for Strings within Files

grep string file(s) Display lines containing string in file(s)
grep -v string file(s) Display lines that do not contain string

Printing
lp file Print file to default printer
lpr file Print file to default printer
lpstat Check status of printer queue
lpstat -p Check status of all printer queues
lpq Check contents printer queue
lprm job# Remove job from printer queue
lprm - Remove all your jobs from printer queue
lp -Pprinter file Print to a specific printer queue
ls -l | lp Print directory listing
head file | lp Print first 10 lines of file
Redirect Output
cmd | lp Direct cmd output to printer
cmd > file Direct cmd output to file
cmd | tee file Direct output to screen and file
cmd >> file Direct cmd output to end of file
cmd1 | cmd2 Direct cmd1 output to input of cmd2
Conditional Execution
cmd1 && cmd2 Execute cmd2 only if cmd1 is successful
cmd1 || cmd2 Execute cmd2 only if cmd1 fails

BACKGROUND PROCESSES
Command Effect

cmd& Run job in background
jobs List jobs running in background in current shell session
fg Bring most recent background job into foreground
fg job# Bring job# into foreground
bg Put job into background
bg job# Put job# into background
Ctrl-z Suspend current job and put it in background (resume with fg or bg)
at timespec cmd
Ctrl-d Execute commands at a specified time
batch cmd Ctrl-d Execute commands in the batch queue
atq Display jobs running in at and batch queues
atrm job# Remove job from at or batch queue

Checking Processes

ps Display current shell processes
ps -ef Display all processes
ps -ef | grep username Display all processes for a user
kill -9 PID Stop a process
Disk Space, User and Environment Information
du -sk Display disk space of current directory in 1024k blocks
du -sk dir Display disk space of dir in 1024k blocks
df -k Display data for mounted file systems
env Display environment variable settings
setenv ENV-VAR XXX Set an environment variable
alias Display all defined aliases
umask Display current default file protection mask
whoami Display your username
id Display your user and group ids
users Display users logged in
groups Display which groups you belong to
w Display who is logged in and what they are doing