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Bash & shell programming

shell programming bash
interactive tricks & tips shell
TODO [C] use whiptail for ncurses dialogs tuihabit
[2021-01-06] Where is the bash feature to open a command in $EDITOR documented? - Unix & Linux Stack Exchange bashhabit

¶shell programming bash

¶[2017-12-25] boolean return value bash

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

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

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

¶[2017-12-30] iterate over array bash

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

¶assert variable is defined {double square brackets -v} operator bashhabit

¶[2018-04-26] get current script directory bash

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

(might not work on mac)

¶avoid passing flags in shebang (e.g. `#!/bin/bash -eu`) bashhabit

CREATED: [2018-06-21]

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

¶[A] [2015-07-23] `diff <(ls dir1) <(ls dir2)` shell

¶[B] use sigquit {Ctrl-\} to kill processes that are really stuck (when Ctrl-C isn't working) shellhabit

CREATED: [2018-03-05]

¶[B] exec command on each file `find . -exec some command {} \;` shelldrill

CREATED: [2019-06-19]

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

CREATED: [2019-06-20]

¶[C] [2018-05-08] `ps aufx` to list all processes shell

¶[C] tree -pufi for file tree with permissions shellhabit

CREATED: [2018-09-18]

¶[C] pretty print json `cat file.json | python -mjson.tool` shelljson

¶[D] detect if library is installed `ldconfig -p | grep libjpeg` or `gcc -ljpeg` shell

¶[D] [2015-07-23] merging pdfs shell

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

¶[D] {ln -i} for interactive symlink (prompts for removal) shellhabit

CREATED: [2018-03-01]

¶TODO [C] use whiptail for ncurses dialogs tuihabit

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

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

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