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

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

Q1

Change directory to root

cd /

Change directory to home

cd ~

Change directory to sub-directory foo (of current directory)

cd foo

List files and directories of the current directory

ls

List files and directories of the current directory, including hidden files, but not the current or parent

ls -A

List files and directories of the current directory sorted by modification time

ls -t

List files and directories of the current directory ???

ls -d

List files and directories of the current directory and show file size in human readable format

ls -h

List files and directories of the current directory and recursively list sub-directories

ls -R

List files and directories of the current directory and sort by file size

ls -S

Control character to move to the beginning of the line

a

Control character to terminate the foreground job

c

Control character to move to the end of the line

e

Control character to erase back to the last white-space character (and save to clipboard)

w

Control character to pause foreground job

z

Control character to erase from the beginning of the line to the cursor (and save to clipboard)

u

Control character to erase from the cursor to the end of the line (and save to clipboard)

k

Control character to move back one character

b

Control character to move forward one character

f

Control character that is the same as Enter

j

Control character to move to next in history (same as down)

n

Control character to move to previous in history (same as up)

p

Control character to enter the current command then put it back in the command line (for further editing)

o

Control character to paste

y