syntactic sugar

reference:
ppo/gist/bash.md
Unix / Linux - Shell Substitution
ShellCheck Wiki Sitemap
* cd is not a program

oneline commands

[!TIP]
iMarslo : kubernetes - oneline cmd
johnnypea/useful-one-liners.sh
ITT: Post useful shell aliases/functions
Post your handy self made command line utilities

cat and EOF

[!NOTE|label:references:]

Chapter 19. Here Documents

bash Heredoc

using heredoc with ssh

ssh -T user@host.com << EOF
echo "The current local working directory is: $PWD"
echo "The current remote working directory is: \$PWD"
EOF

* POSIX.1 states

...an operand naming a file can be specified as '-', which means to use the standard input instead of a named file ....

kubectl apply from stdin

[!NOTE|label:references:]
Need some explaination of kubectl stdin and pipe

$ cat << 'EOF' | kubectl apply -f -
...
...
EOF

# or
$ kubectl apply -f - << EOF
...
...
EOF

git apply from stdin

$ cat >> 'EOF' | git apply --inaccurate-eof --ignore-whitespace
...
...
EOF

# or
$ git apply --inaccurate-eof --ignore-whitespace --stat << 'EOF'
...
...
EOF
 install |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

git apply from clipboard

[!NOTE|label:references:]
Pipe (a patch in my clipboard) to git apply?

$ pbpaste | git apply

$ xsel --clipboard --input | git apply
# or
$ xclip -selection clipboard -o | git apply

patch from stdin
[!NOTE|label:references:]
- How can I run patch through a heredoc in bash?
```
$ patch --dry-run --ignore-whitespace << 'EOF'
...
...
EOF
```

while read from input

[!NOTE|label:references:]
How to use a shell command to only show the first column and last column in a text file?

$ while IFS=\| read -r col1 col2; do echo ">> $col1 .. $col2 <<"; done <<\INPUT
  a|b
  INPUT
>> a .. b <<

tail and timestamp

$ tail -f file | while read line; do echo -n $(date -u -Ins); echo -e "\t$line"; done

backup multiple files

$ cp -bfS.bak filename filename

ssh

compress and ssh and extract

$ tar cf - . | ssh elsewhere tar xf - -C /other/dir

# or: https://www.commandlinefu.com/commands/view/4034/copy-a-folder-tree-through-ssh-using-compression-no-temporary-files
$ ssh <host> 'tar -cz /<folder>/<subfolder>' | tar -xvz

tips

[!NOTE|label:references:]
How can I copy multiple files over scp in one command?

# tips
$ tar cfz - . | ssh otherhost "cd /mydir; tar xvzf -"

# or: https://www.commandlinefu.com/commands/view/1629/pack-up-some-files-into-a-tarball-on-a-remote-server-without-writing-to-the-local-filesystem
$ tar -czf - * | ssh example.com "cat > files.tar.gz"

# the z-flag to tar does compression. Or you can use -C to ssh:
$ tar cf - . | ssh -C otherhost "cd /mydir; tar xvf -"

find and tar

$ find . -name builds -prune -o -type f -print | tar czf ~/m.tar.gz --files-from -

# or find with maxdepth
$ find . -type f -name "config.xml" -maxdepth 2 -prune -print | tar czf ~/config.xml.130.tar.gz --files-from -

# find with special name
$ find . -name config\.xml -type f -print | tar czf ~/m.tar.gz --files-from -

# and ssh and extract
$ tar cf - . | ssh -C otherhost "cd /mydir; tar xvf -"

for JENKINS_HOME

backup all config.xml in JENKINS_HOME

$ find ${JENKINS_HOME}/jobs \
       -maxdepth 2 \
       -name config\.xml \
       -type f -print |
  tar czf ~/config.xml.tar.gz --files-from -

back build history

$ find ${JENKINS_HOME}/jobs \
       -name builds \
       -prune -o \
       -type f \
       -print |
  tar czf ~/m.tar.gz --files-from -

advanced ls

$ find $PWD -maxdepth 1 -printf '%.5m %10M %#9u:%-9g %#5U:%-5G [%AD | %TD | %CD] [%Y] %p\n'

# or
$ find $PWD -maxdepth 1 -printf '%.5m %10M %#9u:%-9g %#5U:%-5G [%AD | %TD | %CD] [%Y] %p\n' | sort -rgbS 50%

tar and ssh
[!TIP|label:references:]
- * iMarslo: ssh and tar
  copy multiple files to remote server
  tar all and extra in remote
  copy local file content into remote
```
$ tar czv file1 file2 file3 | ssh user@host 'tar xzv -C /target/dir'
```
recursively unrar into dir containing archive
```
$ find . -name '*.rar' -execdir unrar e {} \;
```

find and rename

$ find -iname "*.sh" -exec rename "s/.sh$/.shell/" {} \; -print

find and sort

via timestamp

[!NOTE]
How to Find and Sort Files Based on Modification Date and Time in Linux
$ find . -type f -printf "\n%AD %AT %p" | head -n 11 | sort -k1.8n -k1.1nr -k1
# or
$ find . -type f -printf "\n%Tm/%Td/%TY %TT %p" | sort -k1.8n -k1.1nr -k1
* iMarslo : find printf
* printf time formats
$ find . -printf "%T<format>\n"
sort by datetime format in bash
how to sort file by DD-MM-YYYY dates
Sort logs by date field in bash

# via %T+
$ find ~/.marslo -type f -printf "%10T+ | %p\n" | sort -r | head -10

# via %Td-%Tm-%TY
$ find ~/.marslo -type f -printf "\n%Td-%Tm-%TY %TT %p" |
  sort -b -k1.7,1.10 -k1.4,1.5 -k1.1,1.2 -r

via awk+sort

$ cat a.txt
ABC,1/02/2022,05:50
OPQ,18/10/2023,07:50
HIJ,31/09/2023,08:50
DEF,1/02/2021,06:00

$ awk -F'[,/]' '{printf "%04d-%02d-%02d\t%s\n", $4,$3,$2, $0}' a | sort -r | cut -f2-
OPQ,18/10/2023,07:50
HIJ,31/09/2023,08:50
ABC,1/02/2022,05:50
DEF,1/02/2021,06:00

find and copy

[!TIP]
* iMarslo: find by timestamp

$ find . -type f -newermt '2023-10-16 00:00:00' -exec cp -a --parents -t /path/to/target "{}" \+

# or
$ diff=$(( ($(date --date "24-02-29" +%s) - $(date --date "231016" +%s) )/(60*60*24) ))
$ find . -type f -daystart -mtime -$((diff+1)) -exec cp -a --parents -t /path/to/target "{}" \+

download and extract

[!TIP|label:references:]
* see also: iMarslo: download and extract

$ wget -O - http://example.com/a.gz    | tar xz
# or
$ curl -fsSL http://example.com/a.gz   | tar xz
# or
$ curl -fsSL "http://example.com/a.gz" | tar zxvf -

# or: https://www.commandlinefu.com/commands/view/353/extract-tarball-from-internet-without-local-saving
$ wget -qO - "http://www.tarball.com/tarball.gz" | tar zxvf -

tar.gz

$ curl -fsSL https://dlcdn.apache.org/maven/maven-3/3.9.5/binaries/apache-maven-3.9.5-bin.tar.gz | tar xzf - -C /path/to/targeT

tar.xz

$ curl -fsSL https://ftp.gnu.org/gnu/glibc/glibc-2.38.tar.xz | tar -xJf - -C /path/to/target

zip

$ curl -fsSL https://downloads.gradle.org/distributions/gradle-8.4-bin.zip | bsdtar xzf - -C /path/to/target

# with password
$ curl -fsSL https://path/to/file.zip | bsdtar -xzf- --passphrase <PASSWD_OF_ZIP> - -C <EXTRACT_PATH>

mirror website

$ wget --mirror --page-requisites --html-extension --convert-links $URL

# https://www.linuxjournal.com/content/downloading-entire-web-site-wget
$ wget --recursive --no-clobber --page-requisites --html-extension --convert-links --restrict-file-names=windows --domains website.org --no-parent sample.com

# or download entire website: https://www.commandlinefu.com/commands/view/901/download-an-entire-website
$ wget --random-wait -r -p -e robots=off -U mozilla http://www.example.com

# https://superuser.com/a/1415765/112396
$ wget --recursive --level 5 --no-clobber --page-requisites --adjust-extension --span-hosts --convert-links --restrict-file-names=windows --domains sample.com --no-parent sample.com

# https://www.commandlinefu.com/commands/view/30/retrieve-a-list-of-all-webpages-on-a-site
$ URL=www.example.com && wget -rq --spider --force-html "http://$URL" && find $URL -type d > url-list.txt && rm -rf $URL

download image only

$ wget -r -l1 --no-parent -nH -nd -P/tmp -A".gif,.jpg" http://example.com/images

kubectl apply from stdin

$ cat << EOF | kubectl create -f -
apiVersion: v1
kind: Secret
metadata:
  name: mysecret
type: Opaque
data:
  username: $(echo -n 'admin' | base64)
  password: $(echo -n 'password' | base64)
EOF

show 256 colors

$ for code in {0..255}; do echo -e "\e[38;05;${code}m $code: Test"; done)

# or: https://www.commandlinefu.com/commands/view/6138/show-numerical-values-for-each-of-the-256-colors-in-bash
$ for i in {0..255}; do echo -e "\e[38;05;${i}m${i}"; done | column -c 80 -s ' '; echo -e "\e[m"

# or: https://www.commandlinefu.com/commands/view/11759/show-numerical-values-for-each-of-the-256-colors-in-bash-for-bold-and-normal-fonts
$ for code in $(seq -w 0 255); do for attr in 0 1; do printf "%s-%03s %bTest%b\n" "${attr}" "${code}" "\e[${attr};38;05;${code}m" "\e[m"; done; done | column -c $((COLUMNS*2))
# better vesion
$ for code in $(seq -w 0 255); do for attr in 0 1; do printf "%b%s-%03s%b\n"  "\e[${attr};38;05;${code}m" "${attr}" "${code}" "\e[m"; done; done | column -c $((COLUMNS*3))

# .. zsh ..
# or: https://www.commandlinefu.com/commands/view/5876/show-numerical-values-for-each-of-the-256-colors-in-zsh
$ for code in {000..255}; do print -P -- "$code: %F{$code}Test%f"; done

# or: https://www.commandlinefu.com/commands/view/12471/show-numerical-values-for-each-of-the-256-colors-in-zsh
for i in {0..255}; do echo -e "\e[38;05;${i}m\\\e[38;05;${i}m"; done | column -c 80 -s ' '; echo -e "\e[m"

rm and exclude

$ rm !(*.foo|*.bar|*.baz)

# https://www.commandlinefu.com/commands/view/4576/remove-everything-except-that-file
$ find . ! -name <FILENAME> -delete

# https://www.commandlinefu.com/commands/view/4570/remove-everything-except-that-file
$ ( shopt -s extglob; rm !(<PATTERN>) )

split file to equal size

$ split -b4m file.tgz file.tgz. ; for i in file.tgz.*; do SUBJ="Backup Archive"; MSG="Archive File Attached"; echo $MSG | mutt -a $i -s $SUBJ YourEmail@(E)mail.com

sync mirror

[!NOTE]
How to create public mirrors for CentOS
Configure DNF/Yum Mirror Server

$ rsync -aqzH --delay-updates --delete-after  msync.centos.org::CentOS /path/to/local/mirror/root

# stream 9
$ rsync -aqzH --delay-updates --delete-after rsync.stream.centos.org::CentOS-Stream-All /path/to/local/mirror/root

# or src
$ rsync -aqzH --delay-updates --delete-after rsync.stream.centos.org::CentOS-Stream-nosrc /path/to/local/mirror/root

# exclude debuginfo
$ rsync -aqzH --delay-updates --delete-after rsync.stream.centos.org::CentOS-Stream-nodebug /path/to/local/mirror/root

get all declare

[!NOTE|label:references:]
How to list all variables names and their current values?
What is the difference between source and export?

$ declare
$ declare -p
$ declare -xp

# or
$ typeset
$ typeset -p

# or
$ compgen -v
$ compgen -v | while read line; do echo $line=${!line};done
$ compgen -v | while read line; do declare -p $line; done

# or
$ export
$ printenv

print env

[!NOTE|label:references:]
List all shell variables

$ set -o posix ; set | awk -F '=' '{ print $1 }'

# or
$ env
$ env | awk -F '=' '{ print $1 }'
$ env | awk -F '=' '{ print $1 }' | tr '\n' ' '

# or
$ printenv

using string as variable name

[!NOTE|label:references:]
3.5.3 Shell Parameter Expansion
How to get a variable value if variable name is stored as string?
Dynamic variable names in Bash

eval

$ aa='echo me'
$ var='aa'
$ eval echo \$$var
echo me

${!var}

$ var1="this is the real value"
$ a="var1"
$ echo "${!a}"
this is the real value

more usage

$ sunny='''
\033[38;5;226m    \\   /    \033[0m
\033[38;5;226m     .-.     \033[0m
\033[38;5;226m  ― (   ) ―  \033[0m
\033[38;5;226m     `-’     \033[0m
\033[38;5;226m    /   \\    \033[0m
'''

$ fewClouds='''
\033[38;5;226m   \\  /\033[0m
\033[38;5;226m _ /\"\"\033[38;5;250m.-.    \033[0m
\033[38;5;226m   \\_\033[38;5;250m(   ).  \033[0m
\033[38;5;226m   /\033[38;5;250m(___(__) \033[0m

'''

$ codeMap=(
             ["01"]="sunny"
             ["02"]="fewClouds"
           )
$ icon="$(/usr/bin/curl -sg "https://api.openweathermap.org/data/3.0/onecall?lat=37.3541132&lon=-121.955174&units=metric&exclude=hourly,daily,minutely,alerts&appid=${OWM_API_TOKEN}" | jq -r .current.weather[].icon)"
$ echo ${icon}
02n

$ echo -e "${!codeMap["${icon:0:-1}"]}"

`<<<`, `< <(..)`

[!TIP]
< <( is Process Substitution
The difference between <(...) and >(...) is merely which way the redirections are done

`< <(..)` && `> >(..)`

[!NOTE]

process substitution

syntax

$ command1 < <( command2 )
# equals to
$ command2 | command1

# if read from file, then using `< /path/to/file`

SubShell

example:

$ while read line; do echo "-- ${line} --"; done < <(ls -1)

# equals to: http://mywiki.wooledge.org/BashFAQ/024
$ ls -1 | while read line; do echo "-- ${line} --"; done
# equals to
$ ls -1 | xargs -n1 -i bash -c "echo \"-- {} --\""

# equals to read from file via `< /path/to/file`
$ ls -1 > ls.txt
$ while read line; do echo "-- ${line} --"; done < ls.txt

$ wc < <(date)
    1       6      29

# same as:
$ date | wc
    1       6      29

< <(..)

[!TIP|label:referencs:]

subshell

tips:

# If commandA can read the data from stdin
commandB | commandA                 # You can now get the exit code of commandB from PIPESTATUS.
commandB > >(commandA)              # You can now get the exit code of commandB from $? (or by putting this in an if)

# If commandA cannot read it from stdin, but requires a file argument
commandB > >(commandA <(cat))       # Again, commandB's exit code is available from $?

# You can also keep commandB's output in memory.  When you do this, you can get commandB's exit code from $? or put the assignment in an if
b=$(commandB); commandA <<< "$b"    # Here, commandA reads commandB's output from stdin

common usage

$ diff <(sort list1) <(sort list2)

# or
$ while read file; do
    echo -e "\n\033[1;33m${file}\n---\033[0m"
    sed -n "/<<<<<<< HEAD/,/>>>>>>> /!d;=;p" ${file}
    echo -e "\n\033[1;33m---\033[0m"
  done < <(git grep --no-color -l "<<<<<<< HEAD")

> >(..)
[!TIP]
- Process Substitution
  >(...) is used less frequently; the most common situation is in conjunction with tee(1).
  >(...) is handy when redirecting the output to multiple files, based on some criteria.
```
# For example:
$ some_command | tee >(grep A > A.out) >(grep B > B.out) >(grep C > C.out) > /dev/null
```

parameter substitution

reference:
10.2. Parameter Substitution
* iMarslo: params
How can I keep quotes in Bash arguments?
How can I preserve quotes in printing a Bash script's arguments?

EXPR

DESCRIPTION

${variable-default}

if variable is unset, use default

${variable=default}

if variable is unset, set variable to default

${variable+alt}

if variable is set, use alt, else use null string

${variable:-default}

with ":[-=+]", condition takes also "declared but null"

arguments substitution

reference:
Process all arguments except the first one (in a bash script)
Getting the last argument passed to a shell script
Extract parameters before last parameter in "$@"

EXPR

DESCRIPTION

$@

           p1 p2 p3 p4 p5 p6

${@: 0}

 ./args.sh p1 p2 p3 p4 p5 p6

${@: 1}

           p1 p2 p3 p4 p5 p6

${@: 2}

              p2 p3 p4 p5 p6

${@: 2:1}

p2

${@: 2:2}

              p2 p3

${@: -2}

                       p5 p6

${@: -2:1}

p5

${*: -1} or ${@: $#}

p6

${@: 1:$#-1}

           p1 p2 p3 p4 p5

sample with uncertain parameters

local opt=''
local loop=true
local path params

while ${loop} && [[ $# -gt 0 ]]; do
  case "$1" in
    -*) opt+="$1 "; shift;;
     *) loop=false       ;;
  esac
done

if [[ 1 = "$#" ]]; then
  path=''
  params="$1"
else
  path=${*: -1}
  params=${*:1:$#-1}
fi

echo '---------------- before shift -------------------'
echo ".. \$# : $#"
echo ".. \$@ : $@"
echo ".. \$* : $*"

echo '---------------- after shift -------------------'
opt=''
ss=''
loop=true

while $loop && [[ $# -gt 0 ]]; do
  case "$1" in
    -*) opt+="$1 "; shift;;
     *) loop=false       ;;
  esac
done

echo ".. \$#   : $#"
echo ".. \$@   : $@"
echo ".. \$*   : $*"
echo ".. \$opt : $opt"

if [[ 0 = "$#" ]]; then
  echo -e "\033[0;33mERROR: must provide at least one non-opt param\033[0m"
  exit 2
elif [[ 1 = "$#" ]]; then
  path=''
  params="$1"
else
  path=${*: -1}
  params=${*:1:$#-1}
fi

echo '---------------- result -------------------'
echo ">> opt    : ${opt}"
echo ">> params : ${params}"
echo ">> path   : ${path}"

$ ./c.sh -1 -2 --3-4 a b c d e
---------------- before shift -------------------
.. $# : 8
.. $@ : -1 -2 --3-4 a b c d e
.. $* : -1 -2 --3-4 a b c d e
---------------- after shift -------------------
.. $#   : 5
.. $@   : a b c d e
.. $*   : a b c d e
.. $opt : -1 -2 --3-4
.. $ss  : a b c d e
---------------- result -------------------
>> opt    : -1 -2 --3-4
>> params : a b c d
>> path   : e

$ ./c.sh aa bb
---------------- before shift -------------------
.. $# : 2
.. $@ : aa bb
.. $* : aa bb
---------------- after shift -------------------
.. $#   : 2
.. $@   : aa bb
.. $*   : aa bb
.. $opt :
.. $ss  : aa bb
---------------- result -------------------
>> opt    :
>> params : aa
>> path   : bb

$ ./c.sh -1
---------------- before shift -------------------
.. $# : 1
.. $@ : -1
.. $* : -1
---------------- after shift -------------------
.. $#   : 0
.. $@   :
.. $*   :
.. $opt : -1
ERROR: must provide at least one non-opt param

quotas

${@@Q}

# a.sh
line="${@@Q}"
echo $line

$ bash a.sh -a -b --c='1 2 3'
'-a' '-b' '--c=1 2 3'

# https://stackoverflow.com/a/39463371/2940319
$ expand-q() { for i; do echo ${i@Q}; done; }
$ expand-q -a -b --c='1 2 3'
'-a'
'-b'
'--c=1 2 3'

# https://stackoverflow.com/a/72745869/2940319
function quote() {
  local QUOTED_ARRAY=()
  for ARGUMENT; do
    case ${ARGUMENT} in
      --*=*)
        QUOTED_ARRAY+=( "${ARGUMENT%%=*}=$(printf "%q" "${ARGUMENT#*=}")" )
        shift
      ;;
      *)
        QUOTED_ARRAY+=( "$(printf " %q" "${ARGUMENT}")" )
      ;;
    esac
  done
  echo ${QUOTED_ARRAY[@]}
}

ARGUMENTS="$(quote "${@}")"
echo "${ARGUMENTS}"

printf " %q" "${@}"

[!NOTE]
git-effort

while test -n "$1"; do
  case "$1" in
    -- ) shift; GIT_OPT=$(printf " %q" "${@}"); break ;;
  esac
done
GIT_OPT="${GIT_OPT#\ \'\'}"

# https://stackoverflow.com/a/39463371/2940319
$ params-q() { printf "%q\n" "$@"; }
$ params-q -a -b --c='1 2 3'
-a
-b
--c=1\ 2\ 3

String replacement

[!TIP]
* iMarslo: add ' or " to strings

# a.sh
while test -n "$1"; do
  case "$1" in
    -- ) shift; GIT_OPT="$@";;
    *  ) shift;;
  esac
done

GIT_OPT=$(echo "${GIT_OPT}" |
             sed -r 's/\s+--/\n--/g' |
             sed -r "s/^([^=]+)=(.+)$/\1='\2'/g" |
             sed -e 'N;s/\n/ /'
          )
echo $GIT_OPT

$ bash a.sh -a -b -- --c='1 2 3'
--c='1 2 3'

# https://stackoverflow.com/a/8723305/2940319
# a.sh
C=''
for i in "$@"; do
    i="${i//\\/\\\\}"
    C="$C \"${i//\"/\\\"}\""
done
echo $C

$ bash ~/a.sh -a -b --c='1 2 3'
"-a" "-b" "--c=1 2 3"

string manipulations

reference:
10.1. Manipulating Strings

EXPR

DESCRIPTION

${#string}

length

${string:position}

substring, or positional parameter with $* and $#

${string:position:length}

substring

${string#substring}

deletes shortest match of $substring from front of $string

${string##substring}

same but longest match

${string%substring}

shortest from back

${string%%substring}

longest from back

${string/substring/replacement}

replace first match

${string//substring/replacement}

replace all matches

${string/#substring/replacement}

replace if matches front end of $string

${string/%substring/replacement}

replace if matches back end of $string

${var^}

uppercase first char

${var^^}

uppercase all chars

${var,}

lowercase first char

${var,,}

lowercase all chars

compound comparison

SC2155

problematic code:
```
([ "$x" ] || [ "$y" ]) && [ "$z" ]
```
correct code:
```
{ [ "$x" ] || [ "$y" ]; } && [ "$z" ]
```
example
- git-retag

SC2155

problematic code:
```
export foo="$(mycmd)"
```
correct code:
```
foo="$(mycmd)"
export foo
```

escape code

[!TIP] references:
Color Codes, Escapes & Languages
Escape codes
Escape sequences
Quote and Quote-like Operators

ESCAPE CODE

LANGUAGE

DESCRIPTION

\x1b

Node.js

hex char

\x1b

Node.js w/ TS

hex char

\u001b

Python

hex char

\033

GNU Cpp

octal char

\033

ANSI C

octal char

\033

POSIX-compliant shells

octal char

\e

Bash

\c[

control char

echo

echo var name from variable

[!NOTE]
Chapter 28. Indirect References
3.5.3 Shell Parameter Expansion: {!parameter}
9.2. Typing variables: declare or typeset
sample:
$ foo=bar             # `bar` is the var name
$ bar=baz             # `baz` is the var value

typeset

$ typeset -p "${foo}"$
declare -- bar="baz"

eval \$$

$ eval echo \$$foo
baz

$ echo \$$foo
$bar
# or
$ echo '$'$foo
$bar

{!parameter}
```
$ echo "${!foo}"
baz
```

echo var name

[!NOTE]
Shell: print both variable name and value?
* How to Echo the Variable Name Instead of Variable Value
typeset -p
sample
$ a1='a'
$ a2='aa'
$ c1='c'
$ c2='cc'

typeset
```
$ typeset -p c2
declare -- c2="cc"
```

{!parameter@}

$ echo "${!c@}"
c1 c2

$ echo "${!a@}"
a1 a2

superEcho() {
  echo "$1 = ${!1}"
}

$ superEcho foo
foo = bar
$ superEcho bar
bar = baz

ls

[!NOTE|label:references]
How can I make ls only display files?

# show file only
$ ls -p | command grep -v /

# show folder only
$ ls -p | command grep / | command grep "^."

# show all files ( including hidden )
$ ls -Ap | command grep -v / | command grep "^."

# show all folders ( including hidden )
$ ls -Ap | command grep / | command grep "^."

# show hidden folder only
$ ls -Ap | command grep / | command grep "^\." | command grep "\."

# show hidden file only
$ ls -Ap | command grep -v / | command grep "^\." | command grep "\."

# show all including hidden
$ ls -Ap

# show hidden file and folder
$ ls -Ap | command grep "^\."

bash completion

[!NOTE|label:references]
* iMarslo: bash completion
* iMarslo: bash completion troubleshooting for linux
* iMarslo : _vim()
create bash completion
* Creating a bash completion script
* An introduction to bash completion: part 1
* An introduction to bash completion: part 2
$ complete -W "--help --verbose --version" foo
$ foo --<TAB>
--help
--verbose
--version
8.7 Programmable Completion Builtins
8.6 Programmable Completion
8.8 A Programmable Completion Example
cykerway/complete-alias
Multi Level Bash Completion
List all commands that a shell knows
Integralist/1. bash autocomplete for your custom programs.md
8.6 Programmable Completion : _completion_loader()
8.4.6 Letting Readline Type For You
paths:
osx: $(brew --prefix)/etc/bash_completion.d
completion files in bash-completion@2: $(brew --prefix bash-completion@2)/share/bash-completion/completions/
centos: /usr/share/bash-completion/completions or /etc/bash_completion.d
ubuntu: /usr/share/bash-completion/completions

print existing completion

$ complete -p vim
complete -o bashdefault -o default -F _fzf_opts_completion vim

$ complete -p ffs
complete -o bashdefault -o default -o nosort -F _fd ffs

$ complete -p ff
complete -o bashdefault -o default -o nosort -F _fd ff

remove completion

$ complete -p vim
complete -o bashdefault -o default -F _fzf_opts_completion vim

$ complete -r vim

$ complete -p vim
-bash: complete: vim: no completion specification

list all completions

[!TIP|label:references:]

$ compgen --help
Display possible completions depending on the options

$ complete

# show all commands
$ compgen -c

COMMAND

DESCRIPTION

$ compgen -c

commands

$ compgen -a

aliases

$ compgen -b

built-ins

$ compgen -k

keywords

$ compgen -A function

functions

$ compgen -A function -abck

all above

$ complete
complete -o default -F _quotaon quotaon
complete -o default -F _fzf_path_completion mv
complete -F _postcat postcat
complete -o default -o nospace -v -F _fzf_var_completion printenv
complete -o default -F __start_kubectl kcn
complete -F _filedir_xspec mpg321
complete -F _filedir_xspec tex
complete -F _make gmake
complete -o bashdefault -o default -F _fzf_path_completion diff3
complete -o default -F _ansible ansible
complete -o default -F _fzf_path_completion head
complete -o default -F __start_kubectl kt1
complete -o default -F __start_kubectl kt2
complete -o default -F _fzf_path_completion uniq
complete -F _command else
complete -o default -F __start_kubectl kt3
complete -F _ldapdelete ldapdelete
complete -F _configure configure
complete -F _filedir_xspec freeamp
complete -F _lzma lzma
complete -o default -F __start_kubectl kcc
complete -F _filedir_xspec gqmpeg
complete -F _filedir_xspec texi2html
complete -o default -F _complete_groovydoc groovydoc
complete -F _filedir_xspec hbpp
complete -F _xsltproc xsltproc
complete -F _filedir_xspec jadetex
complete -F _docker droot
complete -o default -F _longopt mkfifo
complete -o bashdefault -o default -F _fzf_path_completion svn
complete -o default -F _fzf_path_completion tee
complete -F _javaws javaws
complete -F _mktemp mktemp
complete -F _filedir_xspec rpm2cpio
complete -F _docker dvi
complete -F _make pmake
complete -o default -F _repquota repquota
complete -F _filedir_xspec hbrun
complete -F _autoscan autoscan
complete -o default -F __start_kubectl kubectl
complete -o default -F _screen screen
complete -F _filedir_xspec ps2pdf14
complete -o default -F _fzf_path_completion grep
complete -F _fzf_path_completion vi
complete -F _autoreconf autoheader
complete -F _composite composite
complete -F _fzf_path_completion bat
complete -F _filedir_xspec ps2pdf13
complete -o default -F _longopt objdump
complete -F _filedir_xspec ps2pdf12
complete -o default -F _longopt sha1sum
complete -o default -F _longopt cut
complete -F _filedir_xspec lyx
complete -o bashdefault -o default -F _fzf_path_completion file
complete -F _gcc gpc
complete -F _filedir_xspec latex
complete -o default -F _look look
complete -F _gradle gradlew.bat
complete -o bashdefault -o default -F _fzf_path_completion hx
complete -F _filedir_xspec poedit
complete -F _fzf_path_completion view
complete -o bashdefault -o default -F _fzf_path_completion dirname
complete -F _function typeset
complete -o bashdefault -o default -F _fzf_path_completion hg
complete -F _command nohup
complete -a -F _fzf_alias_completion unalias
complete -F _vipw vipw
complete -g groupdel
complete -F _make gnumake
complete -u groups
complete -F _filedir_xspec chromium-browser
complete -F _filedir_xspec opera
complete -F _filedir_xspec kbabel
complete -F _fzf_host_completion telnet
complete -F _gcc g77
complete -F _filedir_xspec bzme
complete -o bashdefault -o default -F _fzf_complete_ssh ssh
complete -F _command vsound
complete -c which
complete -F _fzf_path_completion tar
complete -o default -F _longopt m4
complete -F _filedir_xspec madplay
complete -o default -F _fzf_opts_completion fzf-tmux
complete -F _docker drm
complete -F _filedir_xspec dviselect
complete -o default -F _fzf_path_completion cp
complete -F _mas mas
complete -F _animate animate
complete -F _man whatis
complete -o default -F _complete_groovysh groovysh.sh
complete -F _filedir_xspec evince
complete -o bashdefault -o default -F _brew brew
complete -F _docker dcleanall
complete -F _filedir_xspec realplay
complete -o default -F _longopt strip
complete -o bashdefault -o default -o nospace -F __git_wrap__gitk_main gitk
complete -v readonly
complete -o nospace -F _fzf_path_completion rsync
complete -F _ctest ctest
complete -o nospace -F _fzf_dir_completion cd
complete -o default -F _complete_groovydoc groovydoc.bash
complete -F _known_hosts showmount
complete -F _filedir_xspec kdvi
complete -o default -F _longopt tac
complete -F _ldapaddmodify ldapmodify
complete -F _filedir_xspec elinks
complete -F _known_hosts fping
complete -o default -F _longopt env
complete -o default -F _quota quota
complete -F _gradle ./gradlew
complete -u chfn
complete -F _docker drp
complete -F _filedir_xspec compress
complete -F _filedir_xspec pdfjadetex
complete -F _filedir_xspec kghostview
complete -F _man man
complete -F _filedir_xspec pbunzip2
complete -o default -F _brctl brctl
complete -c type
complete -F _ldapcompare ldapcompare
complete -F _known_hosts ssh-installkeys
complete -F _filedir_xspec iceweasel
complete -F _filedir_xspec gtranslator
complete -F _fzf_path_completion unzip
complete -o default -F _longopt expand
complete -o default -F _complete_groovyConsole groovyConsole.bash
complete -o bashdefault -o default -o nospace -F _fzf_path_completion git
complete -F _filedir_xspec lrunzip
complete -o default -F _fzf_path_completion ln
complete -F _command aoss
complete -F _docker drps
complete -F _filedir_xspec ggv
complete -F _filedir_xspec oomath
complete -F _filedir_xspec dvipdfmx
complete -o default -F _fzf_path_completion ld
complete -F _fzf_path_completion gunzip
complete -F _filedir_xspec makeinfo
complete -F _filedir_xspec okular
complete -o default -F _complete_groovysh groovysh
complete -F _ldapsearch ldapsearch
complete -F _command xargs
complete -j -P '"%' -S '"' jobs
complete -o default -F _complete_groovy groovy.sh
complete -F _filedir_xspec oowriter
complete -o bashdefault -o default -F _fzf_path_completion emacsclient
complete -F _cpack cpack
complete -o default -F _fzf_path_completion tail
complete -o default -F _longopt unexpand
complete -o default -F _longopt netstat
complete -F _docker dexe
complete -o default -F _fzf_path_completion ls
complete -F _filedir_xspec epiphany
complete -o nospace -F __gio gio
complete -o bashdefault -o default -F _fzf_path_completion nvim
complete -o dirnames -o nospace -F _fzf_dir_completion pushd
complete -F _filedir_xspec acroread
complete -o default -o nospace -v -F _fzf_var_completion unset
complete -F _postmap postalias
complete -F _nmap nmap
complete -o default -F _longopt csplit
complete -F _known_hosts rsh
complete -F _filedir_xspec sxemacs
complete -F _command exec
complete -F _filedir_xspec aviplay
complete -F _ldapmodrdn ldapmodrdn
complete -F _filedir_xspec rgvim
complete -F _chsh chsh
complete -F _autoconf autoconf
complete -o default -F _longopt nm
complete -o default -F _longopt nl
complete -o default -F _complete_grape grape.bash
complete -o nospace -F _user_at_host ytalk
complete -F _fzf_proc_completion kill
complete -F _fzf_path_completion java
complete -F _cmake cmake
complete -u sux
complete -F _cancel cancel
complete -F _filedir_xspec znew
complete -o default -F _complete_groovydoc groovydoc.sh
complete -F _id id
complete -o default -F _longopt paste
complete -F _ldapaddmodify ldapadd
complete -F _docker dip
complete -o bashdefault -F _perldoc perldoc
complete -F _filedir_xspec kwrite
complete -F _root_command really
complete -o default -F _complete_groovyc groovyc.bash
complete -o bashdefault -o default -o nospace -F __git_wrap__tig_main tig
complete -F _filedir_xspec firefox
complete -o bashdefault -o default -F _fzf_path_completion open
complete -F _ip ip
complete -o default -F __start_kubectl klc
complete -F _docker drit
complete -F _filedir_xspec dvipdfm
complete -F _filedir_xspec ly2dvi
complete -F _filedir_xspec oodraw
complete -F _docker drun
complete -F _import import
complete -o default -F __start_kubectl kcswatch
complete -F _gzip pigz
complete -o default -F __start_kubectl kln
complete -F _autoscan autoupdate
complete -F _known_hosts dig
complete -o nospace -F _user_at_host talk
complete -F _filedir_xspec xemacs
complete -F _docker dls
complete -o nospace -F _dd dd
complete -F _jarsigner jarsigner
complete -F _filedir_xspec kpdf
complete -F _man apropos
complete -o default -F _longopt df
complete -F _command eval
complete -F _docker di
complete -F _postsuper postsuper
complete -F _postconf postconf
complete -F _filedir_xspec bibtex
complete -o default -F _pip_completion pip
complete -F _docker dclr
complete -F _postfix postfix
complete -F _fzf_path_completion chown
complete -F _filedir_xspec netscape
complete -o default -F _longopt wget
complete -F _command do
complete -F _cargo cargo
complete -F _gradle gradle
complete -F _pgrep pgrep
complete -F _filedir_xspec gview
complete -F _filedir_xspec lzfgrep
complete -o bashdefault -o default -o nosort -F _fd ffs
complete -F _filedir_xspec lzless
complete -o default -F _fzf_path_completion du
complete -F _renice renice
complete -F _lsof lsof
complete -F _docker dv
complete -F _known_hosts tracepath
complete -o default -F __start_kubectl kit
complete -o default -F _fzf_path_completion wc
complete -F _fzf_path_completion gzip
complete -F _newgrp newgrp
complete -o default -F _ansible-galaxy ansible-galaxy
complete -F _filedir_xspec cdiff
complete -F _fzf_path_completion emacs
complete -F _filedir_xspec zipinfo
complete -F _docker dcleani
complete -F _filedir_xspec google-chrome
complete -F _gcc c++
complete -F _crontab crontab
complete -F _filedir_xspec rview
complete -A shopt shopt
complete -F _docker dcleanc
complete -F _root_command sudo
complete -F _killall pkill
complete -F _fzf_path_completion javac
complete -F _fzf_path_completion ftp
complete -o default -F _longopt uname
complete -o bashdefault -o default -F _rg rg
complete -F _known_hosts ping
complete -F _filedir_xspec wine
complete -F _filedir_xspec galeon
complete -F _filedir_xspec pdflatex
complete -F _docker dex
complete -F _known_hosts rlogin
complete -o default -F _fzf_opts_completion fzf
complete -F _filedir_xspec portecle
complete -o default -F _longopt sha384sum
complete -o default -F _fzf_path_completion rm
complete -F _filedir_xspec modplugplay
complete -F _ri ri
complete -o default -F _quotaoff quotaoff
complete -F _filedir_xspec dillo
complete -F _filedir_xspec fbxine
complete -F _filedir_xspec lokalize
complete -F _root_command gksudo
complete -F _command nice
complete -o default -F _longopt tr
complete -o default -F _npm_completion npm
complete -F _filedir_xspec oocalc
complete -o default -F _complete_groovyc groovyc.sh
complete -F _gradle gradlew
complete -o default -F _longopt sha256sum
complete -F _root_command gksu
complete -F _filedir_xspec qiv
complete -F _chgrp chgrp
complete -F _filedir_xspec ps2pdfwr
complete -o default -F _edquota edquota
complete -F _filedir_xspec harbour
complete -o bashdefault -o default -F _fzf_path_completion basename
complete -o default -F _longopt ptx
complete -F _filedir_xspec dvitype
complete -o nospace -F __gsettings gsettings
complete -F _gradle ./gradlew.bat
complete -F _known_hosts traceroute
complete -F _fzf_path_completion bzip2
complete -j -P '"%' -S '"' fg
complete -o bashdefault -o default -o nosort -F _fd ff
complete -F _convert convert
complete -F _filedir_xspec unpigz
complete -o default -F _complete_groovy groovy
complete -o bashdefault -o default -o nosort -F _fd fd
complete -F _filedir_xspec mozilla
complete -F _filedir_xspec dvips
complete -o default -F _longopt who
complete -F _montage montage
complete -F _complete compgen
complete -F _filedir_xspec ps2pdf
complete -F _filedir_xspec gpdf
complete -F _complete complete
complete -F _filedir_xspec texi2dvi
complete -o dirnames -F _umount umount
complete -F _function function
complete -o bashdefault -o default -F _fzf_path_completion mvim
complete -o default -F _fzf_path_completion less
complete -o default -F _longopt mknod
complete -F _command padsp
complete -F _passwd passwd
complete -F _filedir_xspec kate
complete -F _pkg_config pkg-config
complete -o default -F _longopt bison
complete -F _filedir_xspec mozilla-firefox
complete -F _filedir_xspec kid3-qt
complete -o default -F _longopt od
complete -F _fzf_path_completion bunzip2
complete -o default -o dirnames -F _mount mount
complete -F _function declare
complete -F _filedir_xspec pdftex
complete -F _ag ag
complete -o default -o nospace -F _fzf_var_completion export
complete -F _vipw vigr
complete -o default -F _ansible-doc ansible-doc
complete -F _nslookup nslookup
complete -F _ssh slogin
complete -o nospace -F _alias alias
complete -F _fzf_path_completion gvim
complete -F _filedir_xspec kaffeine
complete -F _stream stream
complete -F _docker drdp
complete -o default -F _complete_grape grape.sh
complete -F _filedir_xspec mpg123
complete -F _fzf_path_completion find
complete -F _filedir_xspec lzegrep
complete -o default -F _ansible-pull ansible-pull
complete -o default -F _longopt split
complete -o bashdefault -o default -F _fzf_path_completion zip
complete -F _ssh autossh
complete -F _filedir_xspec xv
complete -o default -F _longopt fold
complete -F _known_hosts mtr
complete -o bashdefault -o default -F _fzf_path_completion ruby
complete -o nospace -F _fzf_path_completion scp
complete -F _known_hosts ping6
complete -F _filedir_xspec timidity
complete -F _filedir_xspec xdvi
complete -F _filedir_xspec xfig
complete -F _filedir_xspec xpdf
complete -o default -F _longopt indent
complete -o bashdefault -o default -F _fzf_path_completion chmod
complete -o nospace -F _user_at_host finger
complete -o bashdefault -o default -o nospace -F _python_argcomplete pipx
complete -F _ktutil ktutil
complete -F _xz xz
complete -F _filedir_xspec oobase
complete -F _docker dpa
complete -F _fzf_path_completion perl
complete -F _root_command kdesudo
complete -F _docker drmi
complete -F _filedir_xspec ogg123
complete -F _filedir_xspec lzgrep
complete -u w
complete -F _filedir_xspec ee
complete -F _sh sh
complete -o default -F __start_kubectl kubecolor
complete -F _docker dps
complete -F _filedir_xspec gharbour
complete -u su
complete -o default -F _complete_grape grape
complete -o default -F _longopt irb
complete -F _known_hosts host
complete -o default -F __start_kubectl k
complete -o bashdefault -o default -F _fzf_path_completion ex
complete -o default -F _complete_groovyConsole groovyConsole
complete -o nospace -F __gdbus gdbus
complete -F _sysctl sysctl
complete -F _sqlite3 sqlite3
complete -o default -F _iconv iconv
complete -F _command tsocks
complete -F _docker d
complete -F _xmllint xmllint
complete -o default -F _fzf_path_completion diff
complete -F _ldapwhoami ldapwhoami
complete -F _bzip2 pbzip2
complete -F _postmap postmap
complete -o bashdefault -o filenames -F _pandoc pandoc
complete -F _filedir_xspec bzcat
complete -F _filedir_xspec unlzma
complete -F _filedir_xspec dragon
complete -F _xzdec xzdec
complete -o default -F _longopt shar
complete -F _filedir_xspec ooimpress
complete -F _cpio cpio
complete -F _filedir_xspec xanim
complete -o default -F _complete_groovysh groovysh.bash
complete -o default -F _ansible-vault ansible-vault
complete -j -P '"%' -S '"' disown
complete -F _filedir_xspec xine
complete -o default -F _longopt bash
complete -o default -F _longopt md5sum
complete -o bashdefault -o default -F _fzf_path_completion source
complete -F _filedir_xspec amaya
complete -F _filedir_xspec gv
complete -F _make make
complete -o default -F _fzf_path_completion curl
complete -A stopped -P '"%' -S '"' bg
complete -o default -F __start_kubectl kubeproxy
complete -F _filedir_xspec kid3
complete -o nospace -F __gresource gresource
complete -F _filedir_xspec lilypond
complete -o default -F _longopt bc
complete -F _identify identify
complete -F _filedir_xspec modplug123
complete -o default -F __start_kubectl k4
complete -F _pack200 pack200
complete -A binding bind
complete -o default -F _setquota setquota
complete -b builtin
complete -F _unpack200 unpack200
complete -o default -F _quotacheck quotacheck
complete -F _filedir_xspec pbzcat
complete -F _known_hosts tracepath6
complete -o default -F _complete_groovyc groovyc
complete -o default -F _longopt shasum
complete -F _command ltrace
complete -o default -F __start_kubectl k3
complete -F _fzf_path_completion gcc
complete -F __app gapplication
complete -o bashdefault -o default -F _fzf_path_completion xdg-open
complete -o default -F _ansible-playbook ansible-playbook
complete -u write
complete -F _known_hosts traceroute6
complete -F _fzf_path_completion jar
complete -o default -F _longopt date
complete -F _gcc gcj
complete -F _filedir_xspec rgview
complete -o default -F _fzf_path_completion cat
complete -o default -F _fzf_path_completion awk
complete -o default -F _complete_groovyConsole groovyConsole.sh
complete -o default -F _longopt sha512sum
complete -F _filedir_xspec unxz
complete -o default -F _longopt seq
complete -o default -F _longopt mkdir
complete -F _filedir_xspec rvim
complete -o default -F __start_kubectl krn
complete -o default -F _longopt sha224sum
complete -A helptopic help
complete -F _fzf_path_completion sftp
complete -A setopt set
complete -o default -F __start_kubectl krc
complete -F _compare compare
complete -F _tmux tmux
complete -F _ssh_copy_id ssh-copy-id
complete -o default -F _fzf_path_completion sort
complete -o default -F _longopt pr
complete -o default -F _longopt colordiff
complete -o default -F _fzf_path_completion patch
complete -F _fzf_path_completion g++
complete -o bashdefault -o default -F _fzf_path_completion python
complete -F _conjure conjure
complete -F _ldappasswd ldappasswd
complete -F _filedir_xspec playmidi
complete -o default -F __start_kubectl kcEvicted
complete -o default -F _openssl openssl
complete -o default -F _longopt fmt
complete -o default -F _fzf_path_completion sed
complete -F _tcpdump tcpdump
complete -F _javadoc javadoc
complete -F _filedir_xspec lzcat
complete -o default -F _longopt gperf
complete -F _command time
complete -F _filedir_xspec zcat
complete -F _mogrify mogrify
complete -F _display display
complete -F _root_command fakeroot
complete -o default -F _complete_groovy groovy.bash
complete -F _filedir_xspec lynx
complete -u slay
complete -F _filedir_xspec uncompress
complete -F _autoreconf autoreconf
complete -F _filedir_xspec xzcat
complete -o default -F _fzf_dir_completion rmdir
complete -F _filedir_xspec slitex
complete -o bashdefault -o default -F _fzf_opts_completion vim
complete -F _filedir_xspec aaxine
complete -F _filedir_xspec advi
complete -o bashdefault -o default -F _fzf_path_completion more
complete -o default -F _longopt units
complete -F _docker dcleanfull
complete -o default -F _longopt touch
complete -F _filedir_xspec lzmore
complete -F _command then
complete -F _command command
complete -F _docker dkill
complete -o default -F __start_kubectl kd
complete -F _known_hosts fping6
complete -u runuser
complete -F _filedir_xspec dvipdf
complete -o default -F __start_kubectl kc
complete -F _gradle gradle.bat

osx

[!NOTE|label:references:]
Bash Completion
How to Enable Bash Completion on macOS
iMarslo: brew bash-completion@2

$ brew install bash-completion
# or
$ brew install bash-completion@2

# -- add to bash_profile --
$ echo '[[ -r "$(brew --prefix)/etc/profile.d/bash_completion.sh" ]] && source "$(brew --prefix)/etc/profile.d/bash_completion.sh"' >> ~/.bash_profile
$ echo 'command -v brew >/dev/null && source "$(brew --prefix git)"/etc/bash_completion.d/git-*.sh || source "$(brew --prefix git)"/etc/bash_completion.d/git-prompt.sh' >> ~/.bash_profile
# or
$ echo "[ -f /usr/local/etc/bash_completion  ] && . /usr/local/etc/bash_completion" >> ~/.bash_profile
$ cat ~/.bash_profile
[ -f /usr/local/etc/bash_completion ] && . /usr/local/etc/bash_completion

to check link of bash-completion

$ brew unlink bash-completion --dry-run
Would remove:
/usr/local/etc/bash_completion
/usr/local/etc/bash_completion.d/abook
/usr/local/etc/bash_completion.d/ant
...

add more completion files

$ fd --gen-completions bash | sudo tee $(brew --prefix)/etc/bash_completion.d/fd

$ brew search completion
==> Formulae
apm-bash-completion       docker-completion         open-completion           stormssh-completion
bash-completion ✔         fabric-completion         packer-completion         t-completion
bash-completion@2         gem-completion            pip-completion            tmuxinator-completion
boom-completion           gradle-completion ✔       rails-completion          vagrant-completion
brew-cask-completion ✔    grunt-completion          rake-completion           wp-cli-completion
bundler-completion        kitchen-completion        ruby-completion           yarn-completion
cap-completion            launchctl-completion      rustc-completion          zsh-completions
conda-zsh-completion      maven-completion          sonar-completion
django-completion         mix-completion            spring-completion

==> Casks
compositor

linux

enable

if ! shopt -oq posix; then
  if [ -f /usr/share/bash-completion/bash_completion ]; then
    . /usr/share/bash-completion/bash_completion
  elif [ -f /etc/bash_completion ]; then
    . /etc/bash_completion
  fi
fi

add more completion files

$ fd --gen-completions bash | sudo tee /usr/share/bash-completion/completions/fd

centos

$ fd --gen-completions bash | sudo tee /etc/bash_completion.d/fd

completion for alias

[!TIP|label:rerefences:]
* iMarslo: complete-alias
_complete_alias | cykerway/complete-alias
How to work with complete -F _start_kubectl when alias contains --kubeconfig? | How do I get bash completion for command aliases?

download/install

# download bash_completion.sh for kubectl
$ curl -fsSL https://github.com/cykerway/complete-alias/raw/master/complete_alias -o ~/.bash_completion.sh
# or rhel/centos
$ sudo curl -fsSL https://github.com/marslo/dotfiles/raw/main/.marslo/.completion/complete_alias -o /etc/profile.d/complete_alias.sh
# or osx
$ sudo curl -fsSL https://github.com/marslo/dotfiles/raw/main/.marslo/.completion/complete_alias -o $(brew --prefix)/etc/bash_completion.d/complete_alias

$ sudo chmod +x !$

setup for specific alias

$ echo "complete -F _complete_alias <alias>" >> ~/.bash_profile

example

# i.e.: for kubec* ( kubectl or kubecolor )
$ complete -o nosort -o bashdefault -o default -F _complete_alias $(alias | sed -rn 's/^alias ([^=]+)=.+kubec.+$/\1/p' | xargs)

# or
$ alias k=kubectl
$ echo "complete -F _complete_alias k" >> ~/.bash_profile

troubleshooting

-bash: _compopt_o_filenames: command not found
-bash: [: too many arguments

$ ssh bash_completion: _comp_compgen_known_hosts__impl: -F: an empty filename is specified

[!NOTE|label:references:]
Problem with ssh and bash-completion
Autocomplete server names for SSH and SCP
compgen -A hostname | __fzf_list_hosts

clear completion
```
$ complete -r ssh
```

or add into /usr/local/etc/bash_completion.d/ssh or $(brew --prefix)/etc/bash_completion.d/ssh

# https://unix.stackexchange.com/a/181603/29178
_ssh_hosts()
{
    local cur prev opts
    COMPREPLY=()
    cur="${COMP_WORDS[COMP_CWORD]}"
    prev="${COMP_WORDS[COMP_CWORD-1]}"
    opts=$(command grep '^Host' ~/.ssh/config ~/.ssh/config.d/* 2>/dev/null | command grep -v '[?*]' | cut -d ' ' -f 2-)

    COMPREPLY=( $(compgen -W "$opts" -- ${cur}) )
    return 0
}

_ssh()
{
    local cur prev configfile
    local -a config
    # configfile="$HOME/.ssh/config"

    COMPREPLY=()
    _get_comp_words_by_ref -n : cur prev
    #cur=`_get_cword :`
    #prev=`_get_pword`

    _ssh_suboption_check && return 0

    case $prev in
        -F|-i|-S)
            _filedir
            return 0
            ;;
        -c)
            _ssh_ciphers
            return 0
            ;;
        -m)
            _ssh_macs
            return 0
            ;;
        -l)
            COMPREPLY=( $( compgen -u -- "$cur" ) )
            return 0
            ;;
        -o)
            _ssh_options
            return 0
            ;;
        -w)
            _available_interfaces
            return 0
            ;;
        -b)
            _ssh_bindaddress
            return 0
            ;;
    esac

    if [[ "$cur" == -F* ]]; then
        cur=${cur#-F}
        _filedir
        # Prefix completions with '-F'
        COMPREPLY=( "${COMPREPLY[@]/#/-F}" )
        cur=-F$cur  # Restore cur
    elif [[ "$cur" == -* ]]; then
        COMPREPLY=( $( compgen -W '-1 -2 -4 -6 -A -a -C -f -g -K -k -M \
            -N -n -q -s -T -t -V -v -X -v -Y -y -b -b -c -D -e -F \
            -i -L -l -m -O -o -p -R -S -w' -- "$cur" ) )
    else
        # Search COMP_WORDS for '-F configfile' or '-Fconfigfile' argument
        set -- "${COMP_WORDS[@]}"
        while [ $# -gt 0 ]; do
            if [ "${1:0:2}" = -F ]; then
                if [ ${#1} -gt 2 ]; then
                    configfile="$(dequote "${1:2}")"
                else
                    shift
                    [ "$1" ] && configfile="$(dequote "$1")"
                fi
                break
            fi
            shift
        done
        # marslo >> disable _known_hosts_real from $configfile
        # marslo >> using self-defined _ssh_hosts function
        # _known_hosts_real -a -F "$configfile" "$cur"
        _ssh_hosts
        if [ $COMP_CWORD -ne 1 ]; then
            _compopt_o_filenames
            COMPREPLY=( "${COMPREPLY[@]}" $( compgen -c -- "$cur" ) )
        fi
    fi

    return 0
}
shopt -u hostcomplete && complete -F _ssh ssh slogin autossh

$ complete -F _ssh ssh

tricky

alias for sudo

[!TIP|label:references:]
Aliases not available when using sudo
6.6 Aliases

alias sudo='sudo '

get md5sum

get file in tar without exacting

$ tar -O -xf file.tar.gz file.txt | md5sum

# or
$ tar xfO file.tar.gz file.txt | md5sum

get file in zip without extracting
```
$ unzip -p file.zip file.txt | md5sum
```

env

HISTTIMEFORMAT

# https://www.commandlinefu.com/commands/view/3642/save-date-and-time-for-each-command-in-history
export HISTTIMEFORMAT="%h/%d-%H:%M:%S "

# or: YYYY-MM-DD HH:MM:SS : https://www.commandlinefu.com/commands/view/3646/save-date-and-time-for-each-command-in-history
$ export HISTTIMEFORMAT='%F %T '

GREP_OPTIONS

$ GREP_OPTIONS='-D skip --binary-files=without-match --ignore-case'

shortcuts

inserts the results of an autocompletion in the command line
```
$ <command> <kbd>esc</kbd> <kbd>*</kbd>
```
- i.e.: $ echo | -> esc *

man

linux file system
```
$ man hier
```
show ascii
```
$ man ascii
```
ASCII code of key
```
$ showkey -a
```

debugging a script

making xtrace more useful
[!TIP]
- PS4 has to be start with + | and
- 5.2 Bash Variables - PS4
  PS4 The value of this parameter is expanded like PS1 and the expanded value is the prompt printed before the command line is echoed when the -x option is set (see The Set Builtin). The first character of the expanded value is replicated multiple times, as necessary, to indicate multiple levels of indirection. The default is ‘+ ’.
```
$ export PS4='+\033[37;2;3m(${BASH_SOURCE}:${LINENO})\033[0m: \033[35;2;3m${FUNCNAME[0]:+${FUNCNAME[0]}():}\033[0m '
# or
$ export PS4='+(${BASH_SOURCE}:${LINENO}): ${FUNCNAME[0]:+${FUNCNAME[0]}(): }'

# even more:
$ export PS4='Line $LINENO @ $(date +%s.%N): '
```
LINENO and BASH_LINENO
[!NOTE|label:references:]
- Bash Variables BASH_LINENO An array variable whose members are the line numbers in source files where each corresponding member of FUNCNAME was invoked. ${BASH_LINENO[$i]} is the line number in the source file (${BASH_SOURCE[$i+1]}) where ${FUNCNAME[$i]} was called (or ${BASH_LINENO[$i-1]} if referenced within another shell function). Use LINENO to obtain the current line number.
  FUNCNAME An array variable containing the names of all shell functions currently in the execution call stack. The element with index 0 is the name of any currently-executing shell function. The bottom-most element (the one with the highest index) is "main". This variable exists only when a shell function is executing. Assignments to FUNCNAME have no effect. If FUNCNAME is unset, it loses its special properties, even if it is subsequently reset.
  This variable can be used with BASH_LINENO and BASH_SOURCE. Each element of FUNCNAME has corresponding elements in BASH_LINENO and BASH_SOURCE to describe the call stack. For instance, ${FUNCNAME[$i]} was called from the file ${BASH_SOURCE[$i+1]} at line number ${BASH_LINENO[$i]}. The caller builtin displays the current call stack using this information.
```
#!/usr/bin/env bash

function log() {
  echo "LINENO: ${LINENO}"
  echo "BASH_LINENO: ${BASH_LINENO[*]}; LINENO: ${LINENO}"
}

function foo() {
  log "$@"
}

foo "$@"
```
```
# result
$ bash -x debug.sh
+(debug.sh:12):  foo
+(debug.sh:9): foo(): log
+(debug.sh:4): log(): echo 'LINENO: 4'
LINENO: 4
+(debug.sh:5): log(): echo 'BASH_LINENO: 9 12 0; LINENO: 5'
BASH_LINENO: 9 12 0; LINENO: 5
```

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oneline commands

cat and EOF

while read from input

ssh

find and tar

find and rename

find and sort

find and copy

download and extract

kubectl apply from stdin

sync mirror

get all declare

print env

using string as variable name

<<<, < <(..)

< <(..) && > >(..)

parameter substitution

arguments substitution

quotas

string manipulations

compound comparison

escape code

echo

echo var name from variable

echo var name

ls

bash completion

osx

linux

completion for alias

troubleshooting

tricky

alias for sudo

get md5sum

env

shortcuts

man

`<<<`, `< <(..)`

`< <(..)` && `> >(..)`