Bash Commands

Resources

• http://www.ibm.com/developerworks/aix/library/au-unixtext/index.html
• http://ss64.com/bash/

Quizzes

• Folder hierarchy concepts (ls, cd, .., ~, /)
• Basic text manipulation
• File manipulation
• Output direction (>, < |)
• Utils
• More Text manipulation (sort, uniq, nl)
• Processes
• Remote
• Sed
• Grep
• Awk
• rsync
• Scripting

Filename aliasing

• * match 0 or more characters
• ? match any single character
• [abc...] match any enclosed character, hyphen to specify range
• [!abc...] not any character
• ~ home directory of current user
• (a|b) pattern a or b
• f{oo,u}bar generates foobar or fubar
  • echo {1...10} will list numbers 1 through 10
• quoting
  • ": $, ' ", \
  • ': only '

Command Forms

• cmd & - execute in background
• cmd1 ; cmd2 - execute multiple commands
• {cmd1; cmd2;} execute commands as a group in the current shell
• (cmd2; cmd2) execute commands as a group in a subshell (I don't know what this means)
• cmd1 | cmd2 pipe output from cmd2 as intput to cmd 2
• cmd1 `cmd2` use cmd2 output as arguments to cmd1
• cmd > file send output to file and overwrite
• cmd &> file send output and errors to file and overwrite
• cmd >> file send output to file and append
• cmd < file take input for cmd from file
• (date; ls) > file - All output is sent to the file
• cmd | tee files send to standard out and files

Command History

• !! previous command
• !n command n
• !-n command n ago
• !string most recent command that starts with stirng
• !?string[?] most recent command that contains string

Terminal Commands

• cd
• pwd

Special Operations

• <
• >
• |
• >>
• tee
• .
• !!
• -
• ~
• ..
• !

Control Characters

Ctrl

• A: beginning of line
• C: terminate foreground job
• E: end of line
• R: Backward search in history for text in command
• W: Erase backwards to whitespace
• Z: Pauses foreground job
• L: clear the screen
• U: clears everything from the cursor to the beginning of the line
• K: clears everything from the cursor to the end of the line
• T: swap the last two characters before the cursor
• B: move the cursor backward one character
• F: forward one character
• J or M: enter
• N: Next in history (down arrow)
• P: Previous in history (up arrow)
• O: Enter the current command and put in back on the command line for further editing
• Y: Paste from ^W, ^K or ^U like commands

Alt

• B: back one word
• F: forward one word
• D: delete to end of word
• C: capitalize letter at cursor, move to end of word
• U: capitalize from cursor to end of word
• L: make lowercase to end of word
• T: swap current word with previous

Bang

• !! : run last command
• !blah : run last command starting with blah

Text Processing

• tr [options] set1 [set2]
  • alnul, alpha, blank, digit, space, upper
  • lower to upper "tr a-z A-Z"
  • -d: delete, -s:squeeze(repeats the operation until no changes occur), -cs
• uniq
  • unique a file by line
  • -c: print the number of times each line occurred
  • -i: ignore case
  • -d: print only duplicated lines
  • -u: print only unique lines
  • -w N: check only N characters
• sort
  • -b: ignore leading blanks
  • -f: ignore case
  • -r: Reverse
  • -u: unique
• wc
  • Shows the line, word and character count
  • -c: print only the byte count
  • -w: print only the word count
  • -l: print only the newline count
  • Example: grep FIXME *.c | wc -l count all the instance of FIXME in *.c files in the current directory
• fold
  • Wraps lines at a given width, by default, 80
  • -s: break at word boundaries, last blank before the maximum.
  • -w WIDTH: sets width
• nl
  • -b STYLE
    • a: number all lines
    • t: number only nonempty lines
    • n:do not number lines
    • pREGEXP: number only lines that contain a match for REGEXP
• diff
  • Display the difference between two files or corresponding files in two directories
    • 'file1 file2'
    • 'dir1 dir2'
    • 'dir file...'
    • 'file... dir'
    • if file is '-', read standard input
  • -b: ignore changes in white spac
  • -B: ignore changes in blank lines
  • -d: Try hard to find a smaller set of changes
  • -E: ignore changes due to tab expansion
  • -i: ignore case differences
  • -l: paginate with 'pr'
  • -N: treat absent files as empty
  • -r: recursively compare sub-directories
  • -s: report when two files are the same

Other

• ls
  • -a: do no hide entries starting with .
  • -A: same as -a,but hide . and ..
  • -c: sort by change time
  • -d: list directory entries instead of contents
  • -h: print file size in human readable format (1K, 234M)
  • -H: same as -h but use powers of 1000 not 1024
  • -l: use long listing format
  • -m: fill width with a comma separated list of entries
  • -o: use long list without group info
  • -r: reverse order while sorting
  • -R: recursive
  • -S: sort by file size
  • -t: sort by modification time
  • -u: sort by last access time
  • -v: sort by version
• less
  • Display output one screen at a time command | less
  • Most commands can be prefixed with N to perform that operation N times
  • Moving and Jumping
    • e or j: forward one line
    • y or k: back one line
    • f or space: forward one window
    • z: back one window
    • d: forward half window
    • u: back half window
    • q or ZZ: exit
    • g or <: goto first line of the file
    • G or >: goto last line of the file
    • m: mark the current position
      • ': goto a previously marked position
      • : goto the previous position
  • Searching
    • /pattern : search forward for matching line
    • ?pattern : search backwards for matching line
    • n: repeat previous search
    • N: repeat search in opposite direction
    • &pattern : filter showing only lines that include pattern
  • Options
    • -n: use line numbers
    • -s: squeeze multiple blank lines
• cat
  • -s: squeeze multiple blank lines
  • -n: number output lines
• man
• head -Count file
  • Returns Count lines from a file, if Count is not specified it defaults to 10
• tac
  • cat in reverse
• tail -Count file
  • prints Count lines of file, if count is not specified, it displays 10 lines
• rev
• echo
  • -n: Do not print the trailing newline

Power Tools

• sed
• grep
• rsync
• find

Files and Folders

• mv
  • Move or rename a file
    • mv Source Dest
    • mv Source Directory
  • -b: make a backup of each file that would otherwise be overwritten or removed
  • -f: remove existing destination files and never prompt the user
  • -S Suffix: append suffix to each backup file made with -b
  • -u: Do not replace a file with one having an older modification time (update)
• rm
  • Remove files
  • -r: remove contents of directories recursively
• mkdir
  • -m: set permission mode
  • -p: make parent directories as needed
• cp
  • Copy a file
    • cp source dest
    • cp source directory
  • -b: backup files before they are overriden
  • -f: remove existing destinations without prompt
  • -r: copy recursively, non-directories as files
  • -R: copy directories recursivly
• rmdir
  • Removes an empty directory
• chmod
  • Change access permissions
  • -R: change files and directories recursivly
• du
  • Shows the size of a folder
  • -a: all files not just directories
  • -h: human readable

Utils

• cal
  • Displays a calendar
    • cal [ [month] year ]
    • If no arguments are given, the current month is displayed
  • -m: Display monday as the first day of the week
  • -y: display a calendar for the current year
• date
  • Display or change the date
• time
  • Measure the running time of a program
  • time command [args]
  • -o File: writes the output to file
  • -f format: format the output

Remote

• ssh
• screen
• ftp
• ping
• rcp
• scp
• wget

Processes

• bg [PID]
  • Sends a job to the background, if no PID is specified, it's the last job run
• fg [PID]
  • Brings a job to the foreground
• jobs
  • lists jobs
• kill
  • stops a process from running
• ps
• coproc
• nohup
• disown

Scripting

• if
• wait
• case

Calculators

• bc
  • Arbitrary precision calculator
• dc
  • Desktop calculator, uses postfix notation

Other

Check a port (in the example, 22)

 netstat -ano|grep :22|grep ESTABLISHED

Zip

 zip =r dir.zip .

This will recursively zip the directory, including hidden files.