例
#!/usr/bin/env bash NAME="John" echo "Hello $NAME!"
變量
NAME="John" echo $NAME echo "$NAME" echo "${NAME}!"
字符串引號
NAME="John" echo "Hi $NAME" #=> Hi John echo 'Hi $NAME' #=> Hi $NAME
條件執行
git commit && git push git commit || echo "Commit failed"
功能
get_name() { echo "John" } echo "You are $(get_name)"
Shell執行
echo "I'm in $(pwd)" echo "I'm in `pwd`" # Same
條件語句
if [[ -z "$string" ]]; then echo "String is empty" elif [[ -n "$string" ]]; then echo "String is not empty" fi
擴展
echo {A,B}.js {A,B} 與...一樣 A B {A,B}.js 與...一樣 A.js B.js {1..5} 與...一樣 1 2 3 4 5
嚴格的模式
set -euo pipefail IFS=$'\n\t'
參數擴展
基本
name="John" echo ${name} echo ${name/J/j} #=> "john" (substitution) echo ${name:0:2} #=> "Jo" (slicing) echo ${name::2} #=> "Jo" (slicing) echo ${name::-1} #=> "Joh" (slicing) echo ${name:(-1)} #=> "n" (slicing from right) echo ${name:(-2):1} #=> "h" (slicing from right) echo ${food:-Cake} #=> $food or "Cake" length=2 echo ${name:0:length} #=> "Jo" STR="/path/to/foo.cpp" echo ${STR%.cpp} # /path/to/foo echo ${STR%.cpp}.o # /path/to/foo.o echo ${STR##*.} # cpp (extension) echo ${STR##*/} # foo.cpp (basepath) echo ${STR#*/} # path/to/foo.cpp echo ${STR##*/} # foo.cpp echo ${STR/foo/bar} # /path/to/bar.cpp STR="Hello world" echo ${STR:6:5} # "world" echo ${STR:-5:5} # "world" SRC="/path/to/foo.cpp" BASE=${SRC##*/} #=> "foo.cpp" (basepath) DIR=${SRC%$BASE} #=> "/path/to/" (dirpath)
代換
${FOO%suffix} 刪除後綴 ${FOO#prefix} 刪除前綴 ${FOO%%suffix} 刪除長後綴 ${FOO##prefix} 刪除長前綴 ${FOO/from/to} 替換第一場比賽 ${FOO//from/to} 全部替換 ${FOO/%from/to} 替換後綴 ${FOO/#from/to} 替換前綴
長度
${#FOO} 的長度 $FOO
解釋
# Single line comment : ' This is a multi line comment '
子
${FOO:0:3} 子串(位置,長度) ${FOO:-3:3} 來自右邊的子串
默認值
${FOO:-val} $FOO,或者val如果沒有設置 ${FOO:=val} 設置$FOO到val如果沒有設置 ${FOO:+val} val如果$FOO設置 ${FOO:?message} 顯示錯誤消息,如果$FOO未設置則退出
循環
循環基礎
for i in /etc/rc.*; do echo $i done
for循環
for ((i = 0 ; i < 100 ; i++)); do echo $i done
for i in {1..5}; do echo "Welcome $i" done 步長 for i in {5..50..5}; do echo "Welcome $i" done
死循環
while true; do ··· done
行循環
< file.txt | while read line; do echo $line done
函數
定義函數
myfunc() { echo "hello $1" } # Same as above (alternate syntax) function myfunc() { echo "hello $1" } myfunc "John"
參數
$# 參數數量 $* 所有參數 $@ 所有參數,從第一個開始 $1 第一個參數
返回
myfunc() { local myresult='some value' echo $myresult } result="$(myfunc)"
提出錯誤
myfunc() { return 1 } if myfunc; then echo "success" else echo "failure" fi
條件
條件
[[ -z STRING ]] 空字符串 [[ -n STRING ]] 不是空字符串 [[ STRING == STRING ]] 等於 [[ STRING != STRING ]] 不平等 [[ NUM -eq NUM ]] 等於 [[ NUM -ne NUM ]] 不相等 [[ NUM -lt NUM ]] 少於 [[ NUM -le NUM ]] 小於等於 [[ NUM -gt NUM ]] 大於 [[ NUM -ge NUM ]] 大於或等於 [[ STRING =~ STRING ]] 正則表達式 (( NUM < NUM )) 數字條件 [[ -o noclobber ]] 如果啓用了OPTIONNAME [[ ! EXPR ]] 非 [[ X ]] && [[ Y ]] 與 [[ X ]] || [[ Y ]] 或
文件條件
[ -e FILE ]] 存在 [[ -r FILE ]] 可讀 [[ -h FILE ]] 符號鏈接 [[ -d FILE ]] 目錄 [[ -w FILE ]] 可寫 [[ -s FILE ]] 大小> 0字節 [[ -f FILE ]] 文件 [[ -x FILE ]] 可執行文件 [[ FILE1 -nt FILE2 ]] 1比2更新 [[ FILE1 -ot FILE2 ]] 2比1更近 [[ FILE1 -ef FILE2 ]] 相同的文件
例
if ping -c 1 google.com; then echo "It appears you have a working internet connection" fi if grep -q 'foo' ~/.bash_history; then echo "You appear to have typed 'foo' in the past" fi # String if [[ -z "$string" ]]; then echo "String is empty" elif [[ -n "$string" ]]; then echo "String is not empty" fi # Combinations if [[ X ]] && [[ Y ]]; then ... fi # Equal if [[ "$A" == "$B" ]] # Regex if [[ "A" =~ "." ]] if (( $a < $b )); then echo "$a is smaller than $b" fi if [[ -e "file.txt" ]]; then echo "file exists" fi
數組
定義數組
Fruits=('Apple' 'Banana' 'Orange') Fruits[0]="Apple" Fruits[1]="Banana" Fruits[2]="Orange"
使用數組
echo ${Fruits[0]} # Element #0 echo ${Fruits[@]} # All elements, space-separated echo ${#Fruits[@]} # Number of elements echo ${#Fruits} # String length of the 1st element echo ${#Fruits[3]} # String length of the Nth element echo ${Fruits[@]:3:2} # Range (from position 3, length 2)
操作
Fruits=("${Fruits[@]}" "Watermelon") # Push Fruits+=('Watermelon') # Also Push Fruits=( ${Fruits[@]/Ap*/} ) # Remove by regex match unset Fruits[2] # Remove one item Fruits=("${Fruits[@]}") # Duplicate Fruits=("${Fruits[@]}" "${Veggies[@]}") # Concatenate lines=(`cat "logfile"`) # Read from file
迭代
for i in "${arrayName[@]}"; do echo $i done
字典
定義
declare -A sounds sounds[dog]="bark" sounds[cow]="moo" sounds[bird]="tweet" sounds[wolf]="howl"
使用詞典
echo ${sounds[dog]} # Dog's sound echo ${sounds[@]} # All values echo ${!sounds[@]} # All keys echo ${#sounds[@]} # Number of elements unset sounds[dog] # Delete dog
迭代
迭代value for val in "${sounds[@]}"; do echo $val done 迭代鍵 for key in "${!sounds[@]}"; do echo $key done
選項
選項
set -o noclobber # Avoid overlay files (echo "hi" > foo) set -o errexit # Used to exit upon error, avoiding cascading errors set -o pipefail # Unveils hidden failures set -o nounset # Exposes unset variables
全局選項
set -o nullglob # Non-matching globs are removed ('*.foo' => '') set -o failglob # Non-matching globs throw errors set -o nocaseglob # Case insensitive globs set -o globdots # Wildcards match dotfiles ("*.sh" => ".foo.sh") set -o globstar # Allow ** for recursive matches ('lib/**/*.rb' => 'lib/a/b/c.rb')
歷史
命令
history 顯示歷史
shopt -s histverify 不要立即執行擴展結果
操作
!! 再次執行最後一個命令 !!:s/<FROM>/<TO>/ 在最近的命令中替換第一次出現的<FROM>to<TO> !!:gs/<FROM>/<TO>/ 在最近的命令中替換所有出現的<FROM>to<TO> !$:t 僅從最近命令的最後一個參數擴展basename !$:h 從最近命令的最後一個參數擴展目錄 !!並且!$可以替換爲任何有效的擴展。
展開
!$ 展開最近命令的最後一個參數 !* 展開最近命令的所有參數 !-n 展開n最近的命令 !n n在歷史記錄中展開命令 !<command> 展開最近的命令調用 <command>
!!:n 僅從n最近的命令擴展該令牌(命令是0;第一個參數是1) !^ 從最近的命令擴展第一個參數 !$ 從最近的命令擴展最後一個標記 !!:n-m 從最近的命令擴展標記範圍 !!:n-$ n從最近的命令擴展令牌到最後
雜項
數值計算
$((a + 200)) # Add 200 to $a $((RANDOM%=200)) # Random number 0..200
檢查命令
command -V cd #=> "cd is a function/alias/whatever"
錯誤
trap 'echo Error at about $LINENO' ERR 要麼 traperr() { echo "ERROR: ${BASH_SOURCE[1]} at about ${BASH_LINENO[0]}" } set -o errtrace trap traperr ERR
相對路徑
source "${0%/*}/../share/foo.sh"
腳本目錄
DIR="${0%/*}"
定界符
cat <<END hello world END
閱讀輸入
echo -n "Proceed? [y/n]: " read ans echo $ans read -n 1 ans # Just one character
轉到上一個目錄
pwd # /home/user/foo cd bar/ pwd # /home/user/foo/bar cd - pwd # /home/user/foo
子shell
(cd somedir; echo "I'm now in $PWD") pwd # still in first directory
重定向
python hello.py > output.txt # stdout to (file) python hello.py >> output.txt # stdout to (file), append python hello.py 2> error.log # stderr to (file) python hello.py 2>&1 # stderr to stdout python hello.py 2>/dev/null # stderr to (null) python hello.py &>/dev/null # stdout and stderr to (null) python hello.py < foo.txt # feed foo.txt to stdin for python
案例/開關
case "$1" in start | up) vagrant up ;; *) echo "Usage: $0 {start|stop|ssh}" ;; esac
打印
printf "Hello %s, I'm %s" Sven Olga #=> "Hello Sven, I'm Olga
獲得選擇
while [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in -V | --version ) echo $version exit ;; -s | --string ) shift; string=$1 ;; -f | --flag ) flag=1 ;; esac; shift; done if [[ "$1" == '--' ]]; then shift; fi
特殊變量
$? 退出上次任務的狀態 $! 最後一個後臺任務的PID $$ shell的PID