bash: Getting Started

Use these commands to dig up more info on command commandname:

$ which -a commandname

$ whereis commandname

$ type commandname

$ type commandname -a

You can also run either -h or –help on most commands, for a list of available flags.

View a history of commands entered in the shell:

$ history

The man utility is key to finding documentation within your Linux system. Most of these cheat sheets you are reading now, were simply distilled from man pages that are probably already on your machine.

Search for commands matching keyword:

$ man -k keyword

View man pages for command commandname:

$ man commandname

View man pages for command commandname in sec. 7:

$ man 7 commandname

• E / Y (Forward/Backward one line)
• D / U (Forward/Backward half window)
• Space / B (Forward/Backward one window)
• H (Display help file)
• Q (Exit)

• 1 (Executable programs or shell commands)
• 2 (System calls)
• 3 (Library calls)
• 4 (Special files)
• 5 (File formats and conventions)
• 6 (Games)
• 7 (Overviews, conventions, and misc)
• 8 (Super user and sysadmin commands)
• 9 (Kernel routines)

Open new bash shell as a child of current one:

$ bash

Exit current bash shell:

$ exit

Show shells by current user:

$ ps --forest

Show list of installed shells:

$ cat /etc/shell

Opens new shell for user username as child of current shell:

$ su username

You can use who am i to see who you are logged in as. You can bring up more identity info with the commands id and who -uh.

Show present working directory:

$ pwd

Show file tree for path:

$ tree path/

Shows source target of link:

$ readlink -f /path/to/link

$ ls

Display directory listing. Some options include:

• -F (With folders identified)
• -A (With hidden dotfiles)
• -l (Long listing format)
• -lh (Human-readable long listing format)
• -t (Sort by modification time, newest first)
• -C (List by columns)
• -X (Sort alphabetically, by extension)
• -R (Recursive into subdirectories)
• -i (Show inode number)

Determine file type of file filename:

$ file filename

$ cat filename

Display contents of file filename. Some options include:

• -n (Numbers output lines)
• -T (Suppress tab characters)

$ more filename

Similar to cat but pages results.

$ less filename

Similar to more but with vi controls.

Displays last 10 lines of file filename:

$ tail filename

Displays last 3 lines:

$ tail -n 3 filename

Displays first 10 lines of file filename:

$ head filename

Displays first 3 lines:

$ head -n 3 filename

$ sort filename

Displays sorted contents of file. Some options include:

• -n (For sorting numbers correctly)
• -M (For sorting months correctly)
• –output=FILE (Spits results out to file)

Example - Sort password file numerically based on column 3 (UID):

$ sort -t ':' -k 3 -n /etc/passwd

$ locate

Searches updatedb for files where any part of path matches string.

$ find

Searches filesystem live based on file attributes.

$ grep searchterm filename

Search filename for searchterm and output lines in file where it is found. Some options include:

• -n (Show line numbers on results)
• -v (Output lines that don't match)
• -c (Output a count of result lines)

Searches path for searchterm:

$ grep searchterm path/

Create an empty file named filename:

$ touch filename

Create a new folder named newfolder:

$ mkdir newfolder

Create a new tree of folders at once:

$ mkdir -p newfolder/subfolder/subfolder

$ cp sourcefilename destinationfilename

Copy file. Some options include:

• -f Force any overwrites
• -i Force shell to ask if you want to overwrite
• -n Do not overwrite targets
• -R Recursive into subdirectories

Copy file into destination path:

$ cp sourcefilename destinationpath/

Copy file into pwd:

$ cp /source/filename .

Copy folder:

$ cp -R sourcefolder/ destinationfolder

Copy folder into pwd:

$ cp -R /source/folder/ .

Create hard link in pwd:

$ ln sourcefilename ./linkname

The flag -s creates a symlink instead of hard link.

To rename files, you intuitively use the move command:

$ mv sourcefilename destinationfilename

Move file to another path and rename:

$ mv /path/sourcefilename /anotherpath/destinationfilename

$ rm filename

Delete file. Some options include:

• -f (Force delete)
• -i (Prompt before every removal)
• -d (Remove empty directories)
• -r (Remove directories and contents recursively)

Delete all files within the PWD:

$ rm ./*

Delete all files matching extension .bar within PWD:

$ rm ./*bar

Delete folder:

$ rmdir foldername

rmdir will not delete a folder with contents. Use rm -rf foldername/ to have rm to recursively delete the folder and its contents instead.