Essential Bash Commands and Their Usage

pwd

Report the path for the present working directory (current directory).

ls

List files in the current directory. Usage: ls or ls path

ls -l

Long listing, with information about size, permissions, ownership, etc.

ls -a

List all files, including those that start with a dot (which would normally be hidden).

ls -A

List all files, including those that start with a dot, excluding the implied '.' and '..'.

ls -R

Recursively list all files in subdirectories.

ls -r

List all entries in reverse order.

ls -S

List all entries and sort them by size ascending.

ls -t

List all entries and sort them by modification time ascending.

ls -F

Put a character at the end of filename to indicate its type.

ls -1

List all entries, one entry per line.

cd

Change current directory. Usage: cd path

mkdir

Make a directory. Usage: mkdir path

rm

Remove files and directories. Usage: rm path

rm -r

Recursively remove files and directories.

rm -i

Interactive mode, prompt before removing files.

rm --

Interpret all subsequent parameters as file names rather than options.

cp

Copy one or more files. Usage: cp old file new file or cp file1 file2 ... directory

cp -r

Recursively copy directories.

cp -a

Copies entries preserving links, preserving file attributes if possible, and copies directories recursively.

cp -u

Copies entries, replacing an existing entry only if the source is newer.

mv

Move files to new filenames or new directories. Usage: mv old name new name or cp file directory

mv -f

Removes existing destination files and never prompt the user.

mv -i

Interactive mode, prompt before overwriting anything.

cat

Read one or more files and write them out one after another to standard output.

cat -b

Output file contents, preceding each non-blank line with the corresponding line number.

cat -n

Output file contents, preceding each line with the corresponding line number.

who

Report who is logged in.

exit

Tell your shell to exit (logging you out of a telnet or secure shell connection).

finger

Give information about a user. Usage: finger username

date

Report what time the system thinks it is.

more

Display the contents of a file to the user one page at a time.

less

Like more but better.

less

Usage: less file

man

Provide online documentation for Unix commands, system calls, configuration files and other features. Usage: man command name

man -S n

Look for documentation in section n of the manual. Section 1 is for shell commands, section 2 is for system calls and section 3 is for other functions.

man -k words

Look for man pages about the given keywords

head

Print the first ten lines of each file parameter (or from stdin if no parameter is given). Usage: head file

head -n num

Print the first num lines of the file.

tail

Print the last ten lines of each file parameter (or from stdin if no parameter is given). Usage: tail file

tail -n num

Print the last num lines of the file.

touch

Bring the modification time of a file up to the current time. Also, create an empty file if it doesn't already exist. Usage: touch file

ps

Show currently running processes.

ps -e

Report on every process.

ps -H

Give hierarchical listing of parent/child processes.

ps -l

Give a long listing.

top

Like ps, but give a continuously updating report.

jobs

Show all processes that your shell is keeping up with along with their job numbers (shell builtin).

bg

Move a suspended process into the background (shell builtin). Usage: bg job number

fg

Move a backgrounded or suspended job to the foreground (shell builtin). Usage: fg job number

kill

Send a signal to a process asking it to terminate. Usage: kill process id

killall

Kill all processes running a given command. Usage: killall command name

echo

Just print out its string parameters. Often used with variable expansion to generate output from a shell script. Example: echo "My home is $HOME"

echo -n

Don't automatically print a newline at the end of the output.

env

Report exported environment variables.

grep

Read from files listed on the command line (or stdin) and report lines that match a given pattern. Usage: grep pattern file1 file2 ... Example: grep "printf" test.h test.c

grep -v

Report only lines that don't match the given pattern.

grep -c

Don't report matching lines, just print the number of lines that match in each input file.

grep -E

Interpret pattern as extended regular expression syntax.

grep -i

Ignore case.

grep -n

Prefix each reported match with the line number.

grep -q

Quiet mode. Don't print anything. Just use the exit status to report whether or not a match was found.

grep -o

Show only the part of a matching line that matches PATTERN.

find

Recursively search directories to find matching files. By default, just print out matching pathnames. Usage: find path options

find -print

Print out each matching path.

find -type f

Only report matching files.

find -type d

Only report matching directories.

find -mmin -n

Report files modified less than n minutes ago.

find -mmin +n

Report files modified more than n minutes ago.

find -mtime -n

Report files modified less than n days ago.

find -mtime +n

Report files modified more than n days ago.

find -exec command ;

Execute command for each matching file.

stat

Display information about files. Usage: stat options file

stat -c '%s'

Report size in bytes.

stat -c '%U'

Report name of the owner.

stat -c '%G'

Report group ownership of the file.

sort

Sort lines of given file (or stdin) and output them in sorted order. Usage: sort file

sort -n

Interpret each line as a number and sort by magnitude.

sort -r

Sort in reverse order.

wc

Report the number of bytes, words and lines in a file.

wc -c

Just report number of bytes.

wc -w

Just report the number of words.

wc -l

Just report the number of lines.

chmod

Change the permissions on a file or directory. Usage: chmod options file

chmod +x

Add execute permissions.

chmod -w

Remove wrte permissions.

chmod u+w

Add write permissions for the user that owns the file.

chmod g+r

Add read permissions for the group that owns the file.

chmod o-x

Remove execute permissions for others (other than the file's owner or group).

chmod a+r

Add read permissions for everyone.