How to customize bash
InstallFest 2017
Lukáš Bařinka
Ways of customization
Invocation and Configuration Files
Invocation Options
Logout
cat ~/.bash_logout
# ~/.bash_logout: executed by bash(1) when
# login shell exits. When leaving the console
# clear the screen to increase privacy.
if [ "$SHLVL" = 1 ]; then
[ -x /usr/bin/clear_console ] &&
/usr/bin/clear_console -q
fi
Options
- set options
set -o allexport off braceexpand on emacs on set +o set +o allexport set -o braceexpand set -o emacs
- shopt options
shopt autocd off cdspell off cmdhist on shopt -p shopt -u autocd shopt -u cdspell shopt -s cmdhist
Set Options 1
- -a / -o allexport
foo=bar declare -p foo declare -x foo="bar"/tmp - -b / -o notify
sleep 1000 & [1] 20107 kill %1 [1]+ Terminated sleep 1000
Set Options 2
- -e / -o errexit
foo [shell exits]
- -r / -o noglob
echo /* /*
- -k / -o keyword
a=1 bash -c 'declare -p a b' b=2 declare -x a="1" declare -x b="2"
Set Options 3
- -B / -o braceexpand
echo {01..20..2} 01 03 05 07 09 11 13 15 17 19 - -H / -o histexpand
!! echo {01..20..2} 01 03 05 07 09 11 13 15 17 19
Set Options 4
- -C / -o noclobber
> foo > foo bash: foo: cannot overwrite existing file - -o ignoreeof
IGNOREEOF=2 Ctrl + d Use "exit" to leave the shell. Use "exit" to leave the shell.
Set Options 5
- -u / -o nounset
: $a $b $c; foo bash: a: unbound variable - -t / -o onecmd
pwd; sleep 5 /tmp [shell exits after 5 seconds]
Set Options 6
- -P / -o physical
ln -s ~ /tmp/h cd /tmp/h/.. ; pwd /home - -o pipefail
grep :/var/ruuun/ /etc/passwd | wc -l 0 echo $? 1
Set Options 7
- -x / -o xtrace
echo $(( $(echo $(( $(date +%s) + 3600)) \ | wc -c ) - 1)) ++ wc -c +++ date +%s ++ echo 1488498282 + echo 10 10 - -o vim / -o emacs
Shell Options 1
- autocd
/tmp cd -- /tmp - cdable_vars
foo=/var/tmp cd foo /var/tmp
- cdspell
cd /tpm /tmp - checkjobs
sleep 100 & [1] 27819 exit There are running jobs. [1]+ Running sleep 100 &
Shell Options 2
- cmdhist — bash attempts to save all lines of a multiple-line command in the same history entry
while sleep 1; do date done while sleep 1; do date; done - direxpand
foo=/var/tmp ls $foo tab ls /var/tmp
Shell Options 3
- dirspell
cd /tpm/ tab cd /tmp/ - dotglob
echo * .aptitude .bash_history .bash_logout .bashrc .blender ... - expand_aliases
Shell Options 4
- extglob
rm img+([0-9]).jpg rm img!(+([0-9]).jpg rm img*.@(jpg|png|gif) - failglob
echo fi*le bash: no match: fi*le
Shell Options 5
- force_fignore — suffixes specified by the $FIGNORE cause words to be ignored
FIGNORE=.swp:.tmp:~
ls tab
touch {a..z} {A..Z}
echo [a-z]
a b c d ...
Shell Options 6
- globstar
mkdir -p /var/tmp/a/b/c file /var/tmp/a/** /var/tmp/a/: directory /var/tmp/a/b: directory /var/tmp/a/b/c: directory
Shell Options 7
- histappend — history list is appended to the file, rather than overwriting the file
- histverify — resulting line is loaded into the readline editing buffer, allowing further modification
- lithist — multi-line commands are saved to the history with embedded newlines rather than using semicolons
Shell Options 8
- nocaseglob
echo .v* .vim .viminfo .viminfz.tmp .vimrc .VirtualBox - nullglob
mkdir tmp echo tmp/*
Shell Options 9
- progcomp — programmable completion facilities are enabled
- xpg_echo
echo 'a\nb' a b
Variables
Shell Variables 1
- $BASH_CMDS[] (unsetting element has no effect)
BASH_CMDS+=([d]=/usr/bin/date) BASH_CMDS[grep]=/usr/xpg4/bin/grep hash hits command 2 /usr/xpg4/bin/grep 0 /usr/bin/date 1 /usr/bin/man
Shell Variables 2
- $BASH_XTRACEFD
exec 3>/dev/pts/4 BASH_XTRACEFD=3 set -x - $CDPATH
CDPATH=~/Project:/var/www/vhosts cd if17 /home/barinkl/Project/if17
Shell Variables 3
- $EXECIGNORE — (patterns) ignored by command search (completion), except in hash table
EXECIGNORE=*/bz*:*grep* - $FCEDIT
FCEDIT=vim fc
Shell Variables 4
- $FIGNORE — suffices ignored by filename completion
FIGNORE='~:.bak:.tmp' - $GLOBIGNORE — suffices ignored by globbing
GLOBIGNORE=*.bak:*.tmp
Shell Variables 5
- $HISTCONTROL — second and subsequent lines of a multi-line compound command are not tested
HISTCONTROL=ignorespace:ignoredups:erasedups - $HISTFILE, $HISTFILESIZE, $HISTSIZE
# /dev/null disables saving history HISTFILE=~/.bash_history HISTSIZE=500 HISTFILESIZE=$HISTSIZE
Shell Variables 6
- $HISTIGNORE — (patterns) ignored by history
(& = suppresses duplicate entries)HISTIGNORE="&:ls:[bf]g:exit:[ \t]*" - $HISTTIMEFORMAT — adds #TIMESTAMP into history file
HISTTIMEFORMAT='%Y-%m-%d %T'
Shell Variables 7
- $IFS — (patterns) ignored by history
(& = suppresses duplicate entries)IFS=: while read user:pass:uid:gid:comm:home:shell do ... done < /etc/passwd IFS=$' \t\n' - $TMOUT — timeout for read, select and shell
Shell Variables 8
- $LANG, $LC_*
- sorting the results of pathname expansion
- range expressions
- character classes
- equivalence classes
- collating sequences
- number formatting
- data and time formatting
touch {a..z} {A..Z} é ch
export LC_ALL=en_US.utf8
ls [a-z]* | tr -d '\n'
aAbBcCchdDeEéfFg...yYz
export LC_ALL=C
ls [a-z]* | tr -d '\n'
abcchdefghijklmnopqrstuvwxyz
export LC_COLLATE=cs_CZ.utf8 LC_CTYPE=cs_CZ.utf8
ls [[:lower:]]* | tr -d '\n'
abcdeéfghchijklmnopqrstuvwxyz
Shell Variables 9
- $PS0 — after reading a command and before the command is executed
PS0='\e[01;40;33m\ $(printf "%${COLUMNS}s" \!)\e[0m\n' - $PS1 — primary prompt
- $PS2 — secondary prompt
- $PS3 — prompt for the select command
- $PS4 — before each command during an execution trace
Shell Variables 10
- $PROMPT_COMMAND — value is executed as a command prior to issuing each primary prompt
export PROMPT_COMMAND='history -a; history -n' PS1='\[\033]0;\u@\h:\w\007\]\u@\h:\w\$ ' - $PROMPT_DIRTRIM — number of trailing directory components to retain when expanding the \w and \W string escapes
PROMPT_DIRTRIM=1; cd /var/log/apache2 user@host:.../apache2 >
Aliases
- $BASH_ALIASES[]
BASH_ALIASES+=([sl]=ls [..]='cd ..')
alias c='cd '
alias p='~/Documents/Work/Projects'
c p
cd ~/Documents/Work/Projects
For almost every purpose,
aliases are superseded by shell functions.
Functions
function command_not_found_handle {
if [ -x /usr/lib/command-not-found ]
then
/usr/lib/command-not-found -- "$1"
return $?
elif [ -x /usr/share/command-not-found/command-not-found ]
then
/usr/share/command-not-found/command-not-found -- "$1"
return $?
else
printf "%s: command not found\n" "$1" >&2
return 127
fi
}
builtin / command
- builtin
function cd { echo "From: $PWD" >&2 builtin cd "$@" echo "To: $PWD" >&2 }
builtin / command
- builtin
function du { command du -sh "$@" \ | egrep '^([0-9.]+G|([5]|1[0-9])[0-9][0-9]M)' }
Traps
stty — Set Teletype
stty -a | sed -n 2,4p
intr = ^C; quit = ^\; erase = ^?; kill = ^U;
eof = ^D; eol = <undef>;
eol2 = <undef>; swtch = <undef>; start = ^Q;
stop = ^S; susp = ^Z; rprnt = ^R;
werase = ^W; lnext = ^V; discard = ^O; ...
stty intr ^T
Disown shell job
xclock &
[1] 21157
jobs
[1]+ Running xclock &
disown %1
jobs
PS0 and Trap on DEBUG
trap 'echo DEBUG' DEBUG
PS0=$'PS0\n'
pwd; echo .
PS0
DEBUG
/home/barinkl
DEBUG
.
DEBUG
Readline
Bind Keys to Actions
showkey -a F2
Press any keys - Ctrl-D will terminate this ...
^[OQ 27 0033 0x1b
79 0117 0x4f
81 0121 0x51
Ctrl+V F2
^[OQ
bind "\"\eOQ\":\"git commit -am ''\e[D\""
bind -x '"\ez":"date"'
Readline Configuration
set blink-matching-paren on
set expand-tilde on
set keyseq-timeout 500
"\C-t": forward-search-history
"##": insert-comment
"\C-o": "> /dev/null"
"\ez": "date\n"
"\eOQ": "git commit -am ''\e[D"
Enable Built-in Command
finfo vs stat
time for ((i=0;i<1000;i++))
do
finfo -m . stat -c %Y .
done >/dev/null
real 0m0,005s real 0m0,768s
user 0m0,004s user 0m0,020s
sys 0m0,000s sys 0m0,164s