Basic file operations

cd directory change into directory
cd /dir1/dir2 change into directory (absolute path)
cd .. move up one directory
pwd print current directory
ls list files in current directory
ls –a list hidden files (eg .login)
ls –l long list (details) of current directory
ls –lrt list files with most recently modified at bottom

cat file show contents of file
more file show contents of file to screen:
<return> to advance one line
<space> to advance one page

head file show first ten lines of file
tail file show last ten lines of file

touch file create file (empty)
mkdir dir create a directory called dir

cp file1 file2 make a copy of file1 called file2
cp file directory copy file into directory
cp file /dir/dir2 copy file into directory (absolute path)
cp /dir/file . copy file from /dir to current directory (.)
cp –r dir1 dir2 copy directory dir1 and its contents to dir2

mv file1 file2 rename file1 as file2
mv file dir move file to directory dir
mv file /dir1/dir2 move file to directory dir2 (absolute path)
mv /dir/file . move file from ./dir to current directory (.)
mv dir1 dir2 rename dir1 as dir2

rm file removes file
rm –r dir removes dir and all contents
\rm –r dir removes dir and all contents without prompts (careful!)

Metacharacters

*                                   wildcard for any amount of characters
                                    (eg *.exe – any file ending in .exe)

?                                  wildcard for single character

[ ]                                 enclose wildcard ranges
                                    (eg [a-z], [1-9])

Special characters

$var                            The value of variable var

“    “                            preserve whitespace and ignore metacharacters

‘     ‘                             as above but also preserve special characters

`     `                             enclose system commands
                                    (eg  echo Directory is `pwd`)

;                                   Enables multiple commands on one line

(      ) >                        Encloses multiple commands with common output

\                                   Used before a special or metacharacter to ignore its meaning (similar to single quotes)

File and Process Redirection

cmd  >  file                 redirect output to a file
(eg ls > list produces a file called list, containing filenames from current directory)

cmd  >>  file              append output to an existing file
                                    (eg  cat file2 >> file1 adds the text of file2
                                    to the end of file1)

cmd1 | cmd2 pass output from cmd1 to cmd2
(eg ls –l | more lists files to screen, with controls as above for more)

File size and Disk Space

ls –l | sort –n +4       list files, sort numerically by 5th field (byte size)
                                    directories will show as small.

du –ks *                     space used by each file or subdirectory in current directory (size in 1KB blocks)

du –ks * | sort –n     As above, sort numerically

df –h                           display mounted filesystems and space available

Changing Ownership and Permissions

chown  user  file     Change ownership of file to user
chgrp  group  file Change group ownership of  file to group
chown  user:group  file     Do both of the above at once

chmod [ u g o ]+[ r w x ]  file

            Add read, write or execute permissions for user, group or world
            Can be any combination

chmod [ u g o ]-[ r w x ]  file

            Remove read, write or execute permissions for user, group or world
            Can be any combinations

chmod  xyz  file

            Octal file permission for user (x), group (y) and world (z)
            0 ---   1 --x   2 -w-   3 -wx   4 r--   5 r-x   6 rw-   7 rwx

If changing directories instead of files, the –R flag will apply the ownerships and permissions recursively.

 
Process Management

cmd &                        Run command in background

“ctrl + z”                    Suspend current shell command
bg                               Allow suspended command to run in background

ps –e                          List all active processes, process ID and CPU time
ps –ef                         Long list of above
ps –ef | grep exp     List of processes matching expression exp

kill pid                        Kill process number pid
kill –9 pid                   Kill, if above doesn’t work
killall exp                   Kill all processes matching expression exp

top                              Display processes with highest CPU usage

Tools

find . –name file1                Find file called file1 below current directory
find . –name “*exp*”          Find files with names containing exp
find . –name file1 –ls          Find file and display properties

find . –name file1 –exec rm {} \;               Find and delete file1

cat file | mail user@company.com         Mail contents of file to user

history | mail user@company.com        Mail list of recent commands
                                                                        (useful for phone support)

Newer versions of Linux can use the locate command instead of find. It is much better and uses an index file of the system.
Eg. # locate test.tar

Help

man cmd                 Bring up manual pages for cmd
man –k keyword     Show which man pages relate to keyword

IRIX Specific commands

hinv               Display hardware inventory

setmon          change monitor settings
setmon –n 1920x1200_72                        res @ Hz
setmon –x 1920x1200_72                        make permanent

<ctrl + shift + / + F12>         Vulcan Death Grip, kills graphics server

‘xset s on’ turns screen saver on
‘xset s off’ turns screen saver off
‘xset s 300’ turns screen saver on with 300 sec interval