Table of Contents

• [[shell programming]] [[bash]]
  • [2017-12-25] boolean return value
  • [2017-12-26] multi-line string varible
  • [2017-12-30] iterate over array
  • [[assert variable is defined {double square brackets -v} operator]] [[habit]]
  • [2018-04-26] get current script directory
  • [avoid passing flags in shebang (e.g. #!/bin/bash -eu)](#vdpssngflgsnshbnggbnbsh TIDDLYLINK) [[habit]]
• [[interactive tricks & tips]] [[shell]]
  • [2015-07-23] diff <(ls dir1) <(ls dir2)
  • [use sigquit {Ctrl-\} to kill processes that are really stuck (when Ctrl-C isn’t working)](#ssgqtctrltkllprcsssthtrrllystckwhnctrlcsntwrkng TIDDLYLINK) [[habit]]
  • [exec command on each file find . -exec some command {} \;](#xccmmndnchflfndxcsmcmmnd TIDDLYLINK) [[drill]]
  • [exec command in parallel find /path -iname '*.pdf' -print0 | xargs -0 -n1 -i -P8 bash -c "echo 'Processing {}' && command '{}'"](#xccmmndnprlllfndpthnmpdfptxrgsnpbshcchprcssngcmmnd TIDDLYLINK) [[drill]]
  • [2018-05-08] ps aufx to list all processes
  • [[tree -pufi for file tree with permissions]] [[habit]]
  • [pretty print json cat file.json | python -mjson.tool](#prttyprntjsnctfljsnpythnmjsntl TIDDLYLINK) [[json]]
  • [detect if library is installed ldconfig -p | grep libjpeg or gcc -ljpeg](#dtctflbrrysnstlldldcnfgpgrplbjpgrgccljpg TIDDLYLINK)
  • [2015-07-23] merging pdfs
  • [[{ln -i} for interactive symlink (prompts for removal)]] [[habit]]
• [[use whiptail for ncurses dialogs]] [[tui]] [[habit]]
• [2021-01-06] Where is the bash feature to open a command in $EDITOR documented? - Unix & Linux Stack Exchange [[bash]] [[habit]]

Bash & shell programming

shell programming [[bash]]

[2017-12-25] boolean return value

function whatever {
 if (x)
  then
      true
  else
      false
  fi
}
if whatever
then ...

[2017-12-26] multi-line string varible

MULTILINE=$(cat <<-END
here
goes
multi
line
END
)

[2017-12-30] iterate over array

EXTRA_STOWS=("home-arbtt" "home-emacs" "home-anacron")
for s in "${EXTRA_STOWS[@]}"

assert variable is defined {double square brackets -v} operator [[habit]]

[2018-04-26] get current script directory

DIR=$(dirname "$(readlink -f "$0")")

(might not work on mac)

avoid passing flags in shebang (e.g. #!/bin/bash -eu) [[habit]]

e.g. if you specify other flags in terminal, they would override everything
instead, better to use if [[ $0 == "$BASH_SOURCE" ]]; then set -eux; fi

interactive tricks & tips [[shell]]

priorities roughly indicate how useful I find each command

[2015-07-23] diff <(ls dir1) <(ls dir2)

use sigquit {Ctrl-\} to kill processes that are really stuck (when Ctrl-C isn’t working) [[habit]]

exec command on each file find . -exec some command {} \; [[drill]]

exec command in parallel find /path -iname '*.pdf' -print0 | xargs -0 -n1 -i -P8 bash -c "echo 'Processing {}' && command '{}'" [[drill]]

[2018-05-08] ps aufx to list all processes

tree -pufi for file tree with permissions [[habit]]

pretty print json cat file.json | python -mjson.tool [[json]]

detect if library is installed ldconfig -p | grep libjpeg or gcc -ljpeg

[2015-07-23] merging pdfs

pdftk out.pdf j1-process.pdf j1-process-2.pdf j1-process-3.pdf cat output merged.pdf
pdftk full-pdf.pdf cat 1 1 1 2  3 4 12-15 output outfile_p12-15.pdf

{ln -i} for interactive symlink (prompts for removal) [[habit]]

use whiptail for ncurses dialogs [[tui]] [[habit]]

[2021-01-06] Where is the bash feature to open a command in $EDITOR documented? - Unix & Linux Stack Exchange [[bash]] [[habit]]

edit-and-execute-command (C-xC-e)