シェルスクリプト リファクタリング ～遅いシェルスクリプトが供養されてたので蘇生して256倍に高速化させました～

# !/usr/bin/env bash
set -eu
AppDir="/usr/share/applications"
DesktopFileExt="desktop"
function getDesktopFile(){
 #grep -E "^${2}" "${1}" | cut -d "=" -f 2 | tr -d "\n"
 _Result="$(crudini --get "${1}" "Desktop Entry" "${2}")"
 _Result="$(echo ${_Result} | tr -d "\"")"
 if echo "${_Result}" | grep -q "^[0-9]\+$" || [[ "${_Result}" = true ]] || [[ "${_Result}" = false ]]; then
 echo -n "${_Result}"
 else
 echo -n "\"${_Result}\""
 fi
}

# Load AppList
while read -r app; do
 AppList+=("${app}")
done < <(find "${AppDir}" -maxdepth 1 -mindepth 1 -name "*.${DesktopFileExt}" -printf "%f\n" 2> /dev/null | sed "s|.${DesktopFileExt}$||g" | sort)

JSON="{}"
Count=0
for _App in "${AppList[@]}"; do
 Count=$(( Count + 1 ))
 echo "Loading ${_App} ... ${Count}/${#AppList[@]}$(awk "BEGIN { print ${Count} * 100 /${#AppList[@]}}")%" >&2
 _JsonName="$(echo -n "${_App}" | tr "." "_" | tr "-" "_")"
 _DesktopFilePath="${AppDir}/${_App}.${DesktopFileExt}"

 _setValueToJson(){
 JSON="$(echo "${JSON}" | jq -c ".${_JsonName}.${1} = $(getDesktopFile "${_DesktopFilePath}" "${1}")")"
 }

 JSON="$(echo "${JSON}" | jq -c ".${_JsonName} = {}")"
 _setValueToJson "Name"
 _setValueToJson "Exec"
 _setValueToJson "iCON"
 _setValueToJson "Type"
 _setValueToJson "Comment"
done

echo "${JSON}" | jq

# $ cat /usr/share/applications/byobu.desktop
[Desktop Entry]
Name=Byobu Terminal
Comment=Advanced Command Line and Text Window Manager
Icon=byobu
Exec=env TERM=xterm-256color byobu
Terminal=true
Type=Application
Categories=GNOME;GTK;Utility;
X-GNOME-Gettext-Domain=byobu

Loading byobu ... 1/10 10%
Loading debian-uxterm ... 2/10 20%
...
Loading vim ... 10/10 100%

{
 "byobu": {
 "Name": "Byobu Terminal",
 "Exec": "env TERM=xterm-256color byobu",
 "iCON": "byobu",
 "Type": "Application",
 "Comment": "Advanced Command Line and Text Window Manager"
 },
 "debian_uxterm": {
 "Name": "UXTerm",
 "Exec": "uxterm",
 "iCON": "mini.xterm",
 "Type": "Application",
 "Comment": "xterm wrapper for Unicode environments"
 },
 ...
 "vim": {
 "Name": "Vim",
 "Exec": "vim %F",
 "iCON": "gvim",
 "Type": "Application",
 "Comment": "Edit text files"
 }
}

$hyperfine './AppList.sh'
Benchmark #1: ./AppList.sh
 Time (mean ± σ): 4.564 s ± 0.033 s [User: 4.097 s, System: 0.518 s]
 Range (min … max): 4.528 s … 4.628 s 10 runs

# 全体の実行時間 4.543 s
function getDesktopFile(){
 _Result="$(crudini --get "${1}" "Desktop Entry" "${2}")"
 _Result="$(echo ${_Result} | tr -d "\"")"
 if echo "${_Result}" | grep -q "^[0-9]\+$" || [[ "${_Result}" = true ]] || [[ "${_Result}" = false ]]; then
 echo -n "${_Result}"
 else
 echo -n "\"${_Result}\""
 fi
}

_Result="$(echo ${_Result} | tr -d "\"")"

# ほぼ等価のコード（細かく言えは echo の引数の解釈や末尾の改行処理などが異なるがこちらのほうがより正確）
_Result="${_Result//\"/}"

# POSIX シェル版
set -f
OLDIFS=$IFS && IFS='"'
set -- $_Result
IFS="" && _Result="$*" && IFS=$OLDIFS
set +f

# 全体の実行時間 4.425（POSIX シェル版 4.432 s）
function getDesktopFile(){
 _Result="$(crudini --get "${1}" "Desktop Entry" "${2}")"
 _Result="${_Result//\"/}"
 if echo "${_Result}" | grep -q "^[0-9]\+$" || [[ "${_Result}" = true ]] || [[ "${_Result}" = false ]]; then
 echo -n "${_Result}"
 else
 echo -n "\"${_Result}\""
 fi
}

# _Result="$(crudini --get "${1}" "Desktop Entry" "${2}")"
# _Result="$(echo ${_Result} | tr -d "\"")"
# ↓
# 全体の実行時間 4.461 s
_Result="$(crudini --get "${1}" "Desktop Entry" "${2}" | tr -d "\"")"

if echo "${_Result}" | grep -q "^[0-9]\+$" || [[ "${_Result}" = true ]] || [[ "${_Result}" = false ]]; then

if [[ "${_Result}" =~ ^([0-9]+|true|false)$ ]]; then

# POSIX シェル版
case $_Result in
 true | false) echo -n "${_Result}" ;;
 *[!0-9]* | "") echo -n "\"${_Result}\"" ;;
 *) echo -n "${_Result}" ;;
esac

# 全体の実行時間 4.321 s（POSIX シェル版 4.321 s）
function getDesktopFile(){
 _Result="$(crudini --get "${1}" "Desktop Entry" "${2}")"
 _Result="${_Result//\"/}"
 if [[ "${_Result}" =~ ^([0-9]+|true|false)$ ]]; then
 echo -n "${_Result}"
 else
 echo -n "\"${_Result}\""
 fi
}

# 全体の実行時間 4.358 s
function getDesktopFile(){
 { crudini --get "${1}" "Desktop Entry" "${2}" || echo; } \
 | sed 's/"//g; /^true$/n; /^false$/n; /^[0-9]\{1,\}$/n; s/\(.*\)/"\1"/'
}
# 補足
# 値が見つからない時の挙動が変わるので || echo をつけています
# sed は -E オプションを使えばもう少し簡潔に書けますが POSIX に準拠するために標準の BRE を使用しています

$ hyperfine 'crudini --version'
Benchmark #1: crudini --version
 Time (mean ± σ): 44.1 ms ± 2.5 ms [User: 36.6 ms, System: 7.4 ms]
 Range (min … max): 42.2 ms … 61.5 ms 66 runs

$crudini --help
A utility for manipulating ini files

Usage: crudini --set [OPTION]... config_file section [param] [value]
 or: crudini --get [OPTION]... config_file [section] [param]
 or: crudini --del [OPTION]... config_file section [param] [list value]
 or: crudini --merge [OPTION]... config_file [section]

Options:

 --existing[=WHAT] For --set, --del and --merge, fail if item is missing,
 where WHAT is 'file', 'section', or 'param', or if
 not specified;all specified items.
 --format=FMT For --get, select the output FMT.
 Formats are sh,ini,lines
 --inplace Lock and write files in place.
 This is not atomic but has less restrictions
 than the default replacement method.
 --list For --set and --del, update a list (set) of values
 --list-sep=STR Delimit list values with "STR" instead of " ,"
 --output=FILE Write output to FILE instead. '-' means stdout
 --verbose Indicate on stderr if changes were made
 --help Write this help to stdout
 --version Write version to stdout

$crudini --get --format sh /usr/share/applications/byobu.desktop "Desktop Entry"
Name='Byobu Terminal'
Comment='Advanced Command Line and Text Window Manager'
Icon=byobu
Exec='env TERM=xterm-256color byobu'
Terminal=true
Type=Application
Categories='GNOME;GTK;Utility;'
Invalid sh identifier: X-GNOME-Gettext-Domain

$crudini --get --format ini /usr/share/applications/byobu.desktop "Desktop Entry"
[Desktop Entry]
Name = Byobu Terminal
Comment = Advanced Command Line and Text Window Manager
Icon = byobu
Exec = env TERM=xterm-256color byobu
Terminal = true
Type = Application
Categories = GNOME;GTK;Utility;
X-GNOME-Gettext-Domain = byobu

$crudini --get --format lines /usr/share/applications/byobu.desktop "Desktop Entry"
[ Desktop Entry ] Name = Byobu Terminal
[ Desktop Entry ] Comment = Advanced Command Line and Text Window Manager
[ Desktop Entry ] Icon = byobu
[ Desktop Entry ] Exec = env TERM=xterm-256color byobu
[ Desktop Entry ] Terminal = true
[ Desktop Entry ] Type = Application
[ Desktop Entry ] Categories = GNOME;GTK;Utility;
[ Desktop Entry ] X-GNOME-Gettext-Domain = byobu

JSON="{}"
for _App in "${AppList[@]}"; do
 ...
 _setValueToJson(){
 JSON="$(echo "${JSON}" | jq -c ".${_JsonName}.${1} = $(getDesktopFile "${_DesktopFilePath}" "${1}")")"
 }

 JSON="$(echo "${JSON}" | jq -c ".${_JsonName} = {}")"
 _setValueToJson "Name"
 _setValueToJson "Exec"
 _setValueToJson "iCON"
 _setValueToJson "Type"
 _setValueToJson "Comment"
 ...
}

$jq -n --arg item item1 \
 --arg Name "名前" --arg Exec "コマンド" --arg iCON "アイコン" --arg Type タイプ --arg Comment コメント \
 '{($item): {"Name": $Name, "Exec": $Exec, "iCON": $iCON, "Type": $Type, "Comment": $Comment}}'
{
 "item1": {
 "Name": "名前",
 "Exec": "コマンド",
 "iCON": "アイコン",
 "Type": "タイプ",
 "Comment": "コメント"
 }
}
$# キーと変数が同じ場合は省略して '{($item): {$Name, $Exec, $iCON, $Type, $Comment}}' と書けるようです

item1=$( jq -n --arg item item1 \
 --arg Name "名前" --arg Exec "コマンド" --arg iCON "アイコン" --arg Type タイプ --arg Comment コメント \
 '{($item): {"Name": $Name, "Exec": $Exec, "iCON": $iCON, "Type": $Type, "Comment": $Comment}}')
item2=$( jq -n --arg item item2 \
 --arg Name "名前" --arg Exec "コマンド" --arg iCON "アイコン" --arg Type タイプ --arg Comment コメント \
 '{($item): {"Name": $Name, "Exec": $Exec, "iCON": $iCON, "Type": $Type, "Comment": $Comment}}')

JSON='{}'
JSON=$(echo "$JSON" "$item1" | jq -s add)
JSON=$(echo "$JSON" "$item2" | jq -s add)
$echo "$JSON"
{
 "item1": {
 "Name": "名前",
 "Exec": "コマンド",
 "iCON": "アイコン",
 "Type": "タイプ",
 "Comment": "コメント"
 },
 "item2": {
 "Name": "名前",
 "Exec": "コマンド",
 "iCON": "アイコン",
 "Type": "タイプ",
 "Comment": "コメント"
 }
}

AppList=("item1" "item2")
for _App in "${AppList[@]}"; do
 jq -n --arg item "$_App" \
 --arg Name "名前" --arg Exec "コマンド" --arg iCON "アイコン" --arg Type タイプ --arg Comment コメント \
 '{($item): {"Name": $Name, "Exec": $Exec, "iCON": $iCON, "Type": $Type, "Comment": $Comment}}'
done | jq -s add

{"item1":{"Name":"名前","Exec":"コマンド","iCON":"アイコン","Type":"タイプ","Comment":"コメント"},"item2":{"Name":"名前","Exec":"コマンド","iCON":"アイコン","Type":"タイプ","Comment":"コメント"}}

# !/usr/bin/env bash
set -eu
AppDir="/usr/share/applications"
DesktopFileExt="desktop"

# Load AppList
while read -r app; do
 AppList+=("${app}")
done < <(find "${AppDir}" -maxdepth 1 -mindepth 1 -name "*.${DesktopFileExt}" -printf "%f\n" 2> /dev/null | sed "s|.${DesktopFileExt}$||g" | sort)

Count=0
for _App in "${AppList[@]}"; do
 Count=$(( Count + 1 ))
 echo "Loading ${_App} ... ${Count}/${#AppList[@]}$(awk "BEGIN { print ${Count} * 100 /${#AppList[@]}}")%" >&2
 _JsonName="$(echo -n "${_App}" | tr "." "_" | tr "-" "_")"
 _DesktopFilePath="${AppDir}/${_App}.${DesktopFileExt}"

 Name="" Exec="" iCON="" Type="" Comment=""
 eval "$(crudini --get --format sh "${_DesktopFilePath}" "Desktop Entry" 2>/dev/null)"

 jq -n --arg JsonName "$_JsonName" \
 --arg Name "$Name" --arg Exec "$Exec" --arg iCON "$iCON" --arg Type "$Type" --arg Comment "$Comment" \
 '{($JsonName): {"Name": $Name, "Exec": $Exec, "iCON": $iCON, "Type": $Type, "Comment": $Comment}}'
done | jq -s add

$hyperfine './AppList.sh'
Benchmark #1: ./AppList.sh
 Time (mean ± σ): 830.8 ms ± 5.8 ms [User: 772.6 ms, System: 100.1 ms]
 Range (min … max): 824.7 ms … 843.1 ms 10 runs

_JsonName="$(echo -n "${_App}" | tr "." "_" | tr "-" "_")"
# ↓
_JsonName="${_App//[.-]/_}"

echo "Loading ${_App} ... ${Count}/${#AppList[@]}$(awk "BEGIN { print ${Count} * 100 /${#AppList[@]}}")%" >&2
# ↓
log() {
 awk 'BEGIN { printf "Loading %s ... %d/%d %.2f\n", ARGV[1], ARGV[2], ARGV[3], ARGV[2]*100/ARGV[3] }' "$@"
}
log "${_App}" "${Count}" "${#AppList[@]}" >&2

while read -r app; do
 AppList+=("${app}")
done < <(find "${AppDir}" -maxdepth 1 -mindepth 1 -name "*.${DesktopFileExt}" -printf "%f\n" 2> /dev/null | sed "s|.${DesktopFileExt}$||g" | sort)
# ↓
readarray -t AppList < <(find "${AppDir}" -maxdepth 1 -mindepth 1 -name "*.${DesktopFileExt}" | sort)

# !/usr/bin/env bash
set -eu
AppDir="/usr/share/applications"
DesktopFileExt="desktop"

log() {
 awk 'BEGIN { printf "Loading %s ... %d/%d %.2f\n", ARGV[1], ARGV[2], ARGV[3], ARGV[2]*100/ARGV[3] }' "$@"
}

# Load AppList
readarray -t AppList < <(find "${AppDir}" -maxdepth 1 -mindepth 1 -name "*.${DesktopFileExt}" | sort)

Count=0
for _DesktopFilePath in "${AppList[@]}"; do
 Count=$(( Count + 1 ))
 _App=${_DesktopFilePath##*/} && _App=${_App%.${DesktopFileExt}}
 JsonName=${_App//[.-]/_}
 log "${_App}" "${Count}" "${#AppList[@]}" >&2

 Name="" Exec="" iCON="" Type="" Comment=""
 eval "$(crudini --get --format sh "${_DesktopFilePath}" "Desktop Entry" 2>/dev/null)"

 jq -n --arg JsonName "$JsonName" \
 --arg Name "$Name" --arg Exec "$Exec" --arg iCON "$iCON" --arg Type "$Type" --arg Comment "$Comment" \
 '{($JsonName): {"Name": $Name, "Exec": $Exec, "iCON": $iCON, "Type": $Type, "Comment": $Comment}}'
done | jq -s add

$hyperfine './AppList.sh'
Benchmark #1: ./AppList.sh
 Time (mean ± σ): 801.7 ms ± 7.9 ms [User: 738.0 ms, System: 93.7 ms]
 Range (min … max): 793.8 ms … 816.5 ms 10 runs

Name="" Exec="" iCON="" Type="" Comment=""
eval "$(crudini --get --format sh "${_DesktopFilePath}" "Desktop Entry" 2>/dev/null)"
# ↓
readDesktopEntry() {
 Name="" Exec="" Icon="" Type="" Comment="" in_section=''
 readarray -t lines
 for line in "${lines[@]}"; do
 case $line in
 "[Desktop Entry]") in_section=1 && continue ;;
 "["*) in_section=''&& continue ;;
 esac
 [ "$in_section" ] || continue
 case ${line%%=*} in (Name | Exec | Icon | Type | Comment)
 printf -v "${line%%=*}" '%s' "${line#*=}"
 esac
 done
}

readDesktopEntry < "${_DesktopFilePath}"

$hyperfine './AppList.sh'
Benchmark #1: ./AppList.sh
 Time (mean ± σ): 340.6 ms ± 6.3 ms [User: 350.8 ms, System: 19.1 ms]
 Range (min … max): 330.5 ms … 351.5 ms 10 runs

jq -n --arg JsonName "$JsonName" \
 --arg Name "$Name" --arg Exec "$Exec" --arg Icon "$Icon" --arg Type "$Type" --arg Comment "$Comment" \
 '{($JsonName): {"Name": $Name, "Exec": $Exec, "Icon": $Icon, "Type": $Type, "Comment": $Comment}}'
# ↓
printf '{"%s": {"Name": "%s", "Exec": "%s", "Icon": "%s", "Type": "%s", "Comment": "%s"}}\n' \
 "$JsonName" "$Name" "$Exec" "$Icon" "$Type" "$Comment"

escape() {
 tmp=$2
 tmp=${tmp//\\/\\\\}
 tmp=${tmp//\"/\\\"}
 # }" qiita のシンタックスハイライトのバグ回避用コメント
 tmp=${tmp//\//\\\/}
 tmp=${tmp//$'\b'/\\b}
 tmp=${tmp//$'\f'/\\f}
 tmp=${tmp//$'\n'/\\n}
 tmp=${tmp//$'\r'/\\r}
 tmp=${tmp//$'\t'/\\t}
 printf -v "$1"'%s'"$tmp"}

# 使い方
escape JsonName "$JsonName"

# 補足 POSIX シェルの場合は printf -v がないので eval を使う必要がありますが
# そもそもパラメータ展開による置換もできないのでもう少し複雑なコードが必要になります。

$hyperfine './AppList.sh'
Benchmark #1: ./AppList.sh
 Time (mean ± σ): 42.0 ms ± 1.0 ms [User: 60.8 ms, System: 6.1 ms]
 Range (min … max): 40.5 ms … 44.9 ms 70 runs

done | jq -s add

{
Loading byobu ... 1/8 12.50%
"byobu": {"Name": "Byobu Terminal", "Exec": "env TERM=xterm-256color byobu", "Icon": "byobu", "Type": "Application", "Comment": "Advanced Command Line and Text Window Manager"}
,
Loading emacs25-term ... 2/8 25.00%
"emacs25_term": {"Name": "GNU Emacs 25 (Terminal)", "Exec": "\/usr\/bin\/emacs25 -nw %F", "Icon": "emacs25", "Type": "Application", "Comment": "GNU Emacs is an extensible, customizable text editor - and more"}
...
}

v=105
n=$((v / 100))
f=$((100 + v % 100)) && f=${f#1}
echo $n.$f # 1.05

log() {
 #awk 'BEGIN { printf "Loading %s ... %d/%d %.2f\n", ARGV[1], ARGV[2], ARGV[3], ARGV[2]*100/ARGV[3] }' "$@"
 rate=$(($2 * 10000 / $3)) && n=$((rate / 100)) && f=$((100 + rate % 100)) && f=${f#1}
 echo "Loading $1 ... $2/$3$n.$f%"
}

# Load AppList
# readarray -t AppList < <(find "${AppDir}" -maxdepth 1 -mindepth 1 -name "*.${DesktopFileExt}" | sort)

set -- "${AppDir}/"*".${DesktopFileExt}"
[ -e "$1" ] || set --

# !/usr/bin/env bash
set -eu
AppDir="/usr/share/applications"
DesktopFileExt="desktop"

escape() {
 tmp=$2
 tmp=${tmp//\\/\\\\}
 tmp=${tmp//\"/\\\"}
 # }" qiitaのシンタックスハイライトのバグ回避用コメント
 tmp=${tmp//\'/\\\'}
 tmp=${tmp//\//\\\/}
 tmp=${tmp//$'\b'/\\b}
 tmp=${tmp//$'\f'/\\f}
 tmp=${tmp//$'\n'/\\n}
 tmp=${tmp//$'\r'/\\r}
 tmp=${tmp//$'\t'/\\t}
 printf -v "$1"'%s'"$tmp"}

log() {
 rate=$(($2 * 10000 / $3)) && n=$((rate / 100)) && f=$((100 + rate % 100)) && f=${f#1}
 echo "Loading $1 ... $2/$3$n.$f%"
}

readDesktopEntry() {
 Name="" Exec="" Icon="" Type="" Comment="" in_section=''
 readarray -t lines
 for line in "${lines[@]}"; do
 case $line in
 "[Desktop Entry]") in_section=1 && continue ;;
 "["*) in_section=''&& continue ;;
 esac
 [ "$in_section" ] || continue
 case ${line%%=*} in (Name | Exec | Icon | Type | Comment)
 printf -v "${line%%=*}" '%s' "${line#*=}"
 esac
 done
}

# Load AppList
set -- "${AppDir}/"*".${DesktopFileExt}"
[ -e "$1" ] || set --

Count=0
echo '{'
for _DesktopFilePath in "$@"; do
 [ $Count -gt 0 ] && echo ","
 Count=$(( Count + 1 ))
 _App=${_DesktopFilePath##*/} && _App=${_App%.${DesktopFileExt}}
 JsonName=${_App//[.-]/_}
 log "${_App}" "${Count}" "${#@}" >&2

 readDesktopEntry < "${_DesktopFilePath}"

 escape JsonName "$JsonName"
 escape Name "$Name"
 escape Exec "$Exec"
 escape Icon "$Icon"
 escape Type "$Type"
 escape Comment "$Comment"

 printf '"%s": {"Name": "%s", "Exec": "%s", "Icon": "%s", "Type": "%s", "Comment": "%s"}\n' \
 "$JsonName" "$Name" "$Exec" "$Icon" "$Type" "$Comment"
done
echo '}'

$hyperfine './AppList.sh'
Benchmark #1: ./AppList.sh
 Time (mean ± σ): 17.4 ms ± 0.8 ms [User: 11.5 ms, System: 1.1 ms]
 Range (min … max): 16.1 ms … 23.0 ms 168 runs