- Switch to previous directory
- Get global ip
- Simple commands
- Loop
- Loop with specified increment each iteration
- Sequences of letters or numbers
- Reuse arguments
- Reuse commands
- Compare output of two commands
- Fix last command
- Accept interactive commands
- Last exit code
- Easy backup
- Print to stderr
- Debugging
- Useful readline tricks
- Repeat command
- Substrings
- More resources
Switch between the current and previous branch / directory.
$ git branch
* master
development
$ git checkout development
Switched to branch 'development'
$ git checkout - # Switch to previous
Switched to branch 'master'
$ git checkout -
Switched to branch 'development'$ pwd
/
$ cd /tmp
$ cd - # Switch to previous
/
$ cd -
/tmp$ curl ifconfig.co # IPv4
50.110.14.21
$ curl -6 ifconfig.co # IPv6
2010:3f3f:113f:0:ea57:4497:7291:e422Create a script which calls functions by its` first argument. This is very useful to create simple scripts which could be a wrapper for other commands.
#!/usr/bin/env bash
function do_this () { echo "call do_this function"; }
function do_sth() { echo "call do_sth function" }
case "$1" in
do_this|do_sth) "$1" ;;
esacExecute it:
$ ./simple-commands.sh do_this
call do_this functionWrite simple one liner loops if you need to do some batch tasks.
$ for i in {1..10}; do echo "$i"; done
# List disk usage by directories
$ for file in */ .*/ ; do du -sh $file; donefor i in {1..100..2}; do echo $i; done
1
3
5
7
...Brace expansion is great for lots of things.
$ touch file{a..c}
$ ls
$ command ls
filea fileb filec$ touch file-{1..15}
$ ls
file-1 file-10 file-11 file-12 file-13 file-14 file-15 file-2 file-3 file-4 file-5 file-6 file-7 file-8 file-9
$ ls file-{9..12}
file-10 file-11 file-12 file-9$ printf "%s\n" file-{a..c}{1..3}
file-a1
file-a2
file-a3
file-b1
file-b2
file-b3
file-c1
file-c2
file-c3(If you give printf more arguments than it expects, it automatically loops.)
$ ls /tmp
some_file.txt some_archive.tar.gz
$ cd !$
/tmp$ echo "reuse me"
reuse me
$ !!
echo "reuse me"
reuse mediff <(echo "1 2 4") <(echo "1 2 3 4")
1c1
< 1 2 4
---
> 1 2 3 4$ ehco foo bar bar
bash: ehco: command not found
$ ^ehco^echo
foo bar baz $ yes | ./interactive-command.sh
Are you sure (y/n)
Accepted
yes: standard output: Broken pipeThe error message is printed because yes gets killed by SIGPIPE signal. This happens
if the pipe to ./interactive-command.sh gets closed but yes still wants to write into it.
Ignore error message:
$ yes 2>/dev/null | ./interactive-command.sh
$ ls /tmp
some_file.txt
$ echo $?
0$ cp file.txt{,.bak}
$ ls -1
file.txt
file.txt.bak$ >&2 echo hello
hello
Add -xv to your bash scripts, i.e.:
/usr/bin/env bash
set -xv
or /bin/bash -xv script.sh
If you use the standard bash readline bindings.
C-a(akaCTRL+A) move cursor to beginning of lineC-e(akaCTRL+E) move cursor to end of lineM-.(akaALT+.) insert last argument of previous command (like!$, but you can edit it)
Execute a command every two seconds and monitor its` output. This is especially useful for waiting until a deployment or infrastructure provisioning is completed, i.e. on aws.
watch -n2 echo hello
`
$ a="apple orange"
$ echo ${a#* }
orange
$ echo ${a#*p}
ple orange
$ echo ${a##*p}
le orange
$ echo ${a% *}
apple
$ echo ${a%p*}
ap
$ echo ${a%%p*}
a
The # for finding first occurence from the start and % for the first occurence from the end. * for matching any pattern. For greedy matching ## and %%.
- BashFAQ - A full FAQ of useful stuff
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