Bash usage

Usage

2023-03-24 2013-01-31
Loops and constructs
2023-03-24 2013-01-31
Scripting
2023-03-16 2003-03-11
Generic HowTo's
2022-11-24 2008-02-11
Bash documentation
2022-09-08 2016-11-13
HowTo's for text and text files

Bash documentation

2022-11-24 2019-01-24
system variables (aka environment variables + shell variables)
!! !$ $! $# $$ $* $- $0 $? $@ $_ BASH_SOURCE DISPLAY EDITOR H http_proxy HISTFILE HOME HOSTNAME IFS LANG LC_NUMERIC LOGNAME OLDPWD PATH PIPESTATUS PPID PROMPT_COMMAND PS1 PWD RANDOM SHELL SHLVL TMPDIR USER
2022-08-24 2015-02-13
Heredocs
2022-05-20 2013-04-29
(non-)?(login|interactive) shells
2022-02-08 2014-01-10
Curly brackets & shell Brace Expansion
{}
2022-02-08 2009-03-17
Bash wildcards and patterns
2022-01-20
Shell options and arguments
2021-11-13 2017-12-13
WARNING: terminal is not fully functional, Error opening terminal: screen.xterm-256color.
2019-10-23 2010-09-09
Control Bash history with HISTCONTROL
2018-07-10 2011-07-22
Shell exit codes
2017-07-26
-bash: !whatever: event not found, exclamation marks, events, what are these ?
!!
2017-04-11 2014-02-05
Job control
2017-03-20
Bash shortcut keys
2015-12-16 2015-06-10
Regular Expressions in shell context
characters list
2015-09-15
Wildcards and quotes
2015-09-13 2008-02-11
When Bash outputs : -bash: /bin/ls: Argument list too long
2015-05-12
Unset variables in Bash / Ksh
2014-09-09
Why does this {start..stop..step} output {start..stop..step} instead of a sequence of numbers ?
brace expansion
2013-04-25
~/.bashrc is not executed when opening a new SSH session

Generic HowTo's

2023-03-16
How to echo a backspace ?
2022-11-23 2003-03-11
How to compare files ?
2022-02-16 2008-11-26
How to redirect the inputs and outputs of a command ?
fd, file descriptors, stdin, stdout, stderr
2021-03-08 2014-11-17
How to get the IP address of the current host from a script ?
hostname
2021-02-04 2019-10-17
How to display colors in Bash ?
ANSI
2021-01-26 2010-07-20
How to chain shell commands ?
&& || () {}
2021-01-26
How to simulate a ternary operator with command1 && command2 || command3
2020-01-30
How to amend and replay the previous command ?
2019-10-23 2010-09-09
How to customize the shell prompt ?
PS1
2019-09-30 2018-09-20
How to spot a hard link ?
2018-11-08
Read-only TMOUT variable, how to workaround and disable automatic logout ?
2018-10-30
How to write messages specifically to stdout or stderr ?
2018-08-20 2016-11-24
How to cd into a directory among others starting with the same characters ?
2017-09-28 2013-06-02
How to bind a function to a key ?
2017-04-27
How to group shell commands ?
subshell
2017-03-02 2007-09-24
How to handle files which name starts with a dash - ?
2016-01-15 2004-11-09
How to rename numerous files ?
file extension, file name
2015-12-03
How to enter a directory having a special non-printable character in its name ?
2014-02-25
How to run a resource-friendly command ?

Scripting

2023-03-24
How to handle unset variables when the -u / nounset flag is raised ?
2023-03-23 2015-06-10
How to read command-line arguments in a script ?
getopts
2023-03-09 2014-01-01
Bash tests : [ -x ], [ = ], [[ =~ ]], ...
[ [[
2022-09-01
How to feed several variables at once ?
2022-02-16 2018-12-17
How to detect whether a script is run interactively or not ?
2021-03-23 2013-12-04
Bash script flags
set
2021-03-18 2017-09-25
Bash functions
scope
2021-02-09 2015-09-29
How to load tuples in a shell script ?
<<<
2021-01-07 2013-01-31
How to retry until success ?
retry, until
2020-07-08 2015-12-10
Bash arrays
associative, indexed
2019-11-04 2018-11-23
cut vs awk : which is the fastest to extract data from a CSV ?
2019-01-28 2018-07-03
How to convert a relative path into an absolute path to source from anywhere ?
import, include
2018-12-18
How to get a file modification date ?
2018-12-17 2018-11-08
How to write all the outputs of a script into a file ?
2018-11-28
Script error : Bad substitution
2018-11-09 2013-01-31
Bash scripting : using the right shebang
#!/bin/sh, #!/bin/bash, #!/usr/bin/env bash
2018-02-23
How to return a value from a function ?
2017-10-05 2013-01-31
How to check the number of arguments passed to a script ?
2017-03-31 2014-12-10
"Variable variables" a.k.a dynamic variables
2016-11-15
How to interrupt a loop ?
break, continue, eval, exit, return
2016-01-29
How to test if a variable is an integer ?
2015-12-05
Variables holding a path in shell scripts
2015-02-20 2015-02-16
How to use booleans in Bash ?
set, unset

HowTo's for text and text files

2022-09-08
How to trim a line to a specific length ?
2020-10-20 2017-02-23
How to insert a string before / after a line matching a pattern ?
sed
2020-07-08 2014-09-24
How to explode a string into an array ?
2020-06-22 2016-07-04
How to display the nth line after / before a match ?
awk
2020-01-23
How to generate a pin code with a specific length ?
2020-01-14 2015-08-04
How to generate a string made of repetitions of a character / substring ?
2019-12-11
How to alter a line when the previous line matches ?
2019-12-11 2019-03-08
How to remove multi-line comments ?
2019-07-18 2019-05-13
How to get a cascading list of owner + group + permissions for a specified file ?
2019-06-24
How to (re-)indent code automatically ?
2019-04-16
How to count lines matching a regex ?
awk
2019-04-09
How to find duplicate lines in a file ?
2019-02-27 2018-10-30
How to compare code snippets ?
2019-02-15
How to count occurrences of a character in a string ?
2019-01-24
How to escape single quotes within single-quoted strings ?
2019-01-07 2018-12-21
How to concatenate strings ?
+=
2018-12-20 2015-08-19
How to check a string against a list of values ?
case, for, regular expression
2018-12-11
How to match strings across lines ?
2018-12-07 2010-09-27
How to remove newline characters ?
sed
2018-12-06
How to transpose line to column / column to line ?
2018-12-06 2018-08-20
How to read a multiline variable line by line ?
process substitution, < <(...)
2018-11-21
How to remove trailing SPACEs ?
sed
2018-11-05
How to detect duplicate fields in a file ?
awk
2018-10-15
How to remove the line matching a regexp and the following one ?
2018-10-15
How to swap command-line arguments ?
2018-09-03
How to filter lines having duplicate fields ?
awk
2017-10-04
How to get the position of a character in a string ?
2017-04-12 2013-01-31
How to sum numbers ?
bc
2017-03-28
How to round floating numbers ?
awk
2017-03-27
How to display the xth, yth and zth lines of a stream of text ?
2017-03-16 2010-09-27
Negative matching
grep, sed
2017-03-08 2016-11-19
How to keep / remove the n leading / trailing characters of a string ?
2016-12-19 2010-09-27
Extract a substring with a RegExp
sed
2016-12-14
How to display the nth line of a file ?
sed
2016-02-03 2015-06-10
How to compare a variable against a list of characters ?
2016-01-28 2010-09-27
Remove all non-ASCII characters from file/string
sed
2016-01-28 2010-09-27
Remove ANSI colors codes
sed
2016-01-28 2010-09-27
Delete empty lines
sed
2016-01-28 2010-09-27
How to substitute the 1st occurrence only of a pattern in a stream ?
sed
2016-01-28 2010-09-27
Need to handle \n or \t strings ?
sed
2016-01-28 2010-09-27
Replace a string with a newline
sed
2016-01-15
How to perform search / replace on a specific line of a file ?
2015-12-29 2009-11-27
How to handle text file encoding and transcode between us-ascii, iso-8859-15, utf-8, ..., charsets ?
iconv, recode, Emacs
2015-12-15
How to parse a string character by character ?
2015-09-03
How to store a command into a variable ?
eval
2015-04-24 2011-04-01
Convert files between DOS and Unix formats
line endings, dos2unix, tofrodos, unix2dos
2015-02-13 2014-10-17
How to remove the header line from a command output ?
2014-07-31
How to display the n leading / trailing characters from each line of a file ?

Loops and constructs

2023-03-24 2017-10-09
case esac
;; ;& ;;&
2021-06-09 2013-01-31
until
2021-02-12 2013-01-31
for
arithmetic
2019-05-20
while read
2019-05-10
if then else fi