Bash shell one-liners

Series: publications July 22, 2018

Wpis z wykorzystywanymi przeze mnie bardzo często poleceniami podczas pracy z powłoką.

Spis treści

Zbiór poleceń

Reload shell without exit
exec $SHELL -l
Close shell keeping all subprocess running
disown -a && exit
Exit without saving shell history
kill -9 $$
unset HISTFILE && exit
Perform a branching conditional
true && echo success
false || echo failed
Pipe stdout and stderr to separate commands
some_command > >(/bin/cmd_for_stdout) 2> >(/bin/cmd_for_stderr)
Redirect stdout and stderr each to separate files and print both to the screen
(some_command 2>&1 1>&3 | tee errorlog ) 3>&1 1>&2 | tee stdoutlog
List of commands you use most often
history | \
awk '{CMD[$2]++;count++;}END { for (a in CMD)print CMD[a] " " CMD[a]/count*100 "% " a;}' | \
grep -v "./" | \
column -c3 -s " " -t | \
sort -nr | nl |  head -n 20
Quickly backup a file
cp filename{,.orig}
Empty a file (truncate to 0 size)
>filename
Delete all files in a folder that don’t match a certain file extension
rm !(*.foo|*.bar|*.baz)
Pass multi-line string to a file
# cat  >filename ... - overwrite file
# cat >>filename ... - append to file
cat > filename << __EOF__
data data data
__EOF__
Edit a file on a remote host using vim
vim scp://user@host//etc/fstab
Create a directory and change into it at the same time
mkd () { mkdir -p "$@" && cd "$@"; }
Convert uppercase files to lowercase files
rename 'y/A-Z/a-z/' *
printf "%`tput cols`s" | tr ' ' '#'
Show shell history without line numbers
history | cut -c 8-
fc -l -n 1 | sed 's/^\s*//'
Run command(s) after exit session
cat > /etc/profile << __EOF__
_after_logout() {

  username=$(whoami)

  for _pid in $(ps afx | grep sshd | grep "$username" | awk '{print $1}') ; do

    kill -9 $_pid

  done

}
trap _after_logout EXIT
__EOF__
Generate a sequence of numbers
for ((i=1; i<=10; i+=2)) ; do echo $i ; done
# alternative: seq 1 2 10

for ((i=5; i<=10; ++i)) ; do printf '%02d\n' $i ; done
# alternative: seq -w 5 10

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