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变量
NAME="John" echo $NAME echo "$NAME" echo "${NAME}!"
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字符串引号
NAME="John" echo "Hi $NAME" #=> Hi John echo 'Hi $NAME' #=> Hi $NAME 单引号不做解析
-
函数
get_name() { echo "John" } echo "You are $(get_name)"
-
条件执行
git commit && git push git commit || echo "Commit failed"
-
执行命令
echo "I'm in $(pwd)" echo "I'm in `pwd`"
-
条件判断
if [ -z "$string" ]; then echo "String is empty" elif [ -n "$string" ]; then echo "String is not empty" fi
-
花括号展开
echo {A,B}.js => A.js B.js {A,B} 展开就是 A B {A,B}.js 展开就是 A.js B.js {1..5} 展开就是 1 2 3 4 5
-
注释
单行注释用#符号
多行注释用冒号空格单引号 : '任意换行'
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 ${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)
${FOO%suffix} 删除后缀Remove suffix
${FOO#prefix} 删除前缀Remove prefix
${FOO%%suffix} Remove long suffix
${FOO##prefix} Remove long prefix
${FOO/from/to} Replace first match
${FOO//from/to} Replace all
${FOO/%from/to} Replace suffix
${FOO/#from/to} Replace prefix
$((a + 200)) # Add 200 to $a
$((RANDOM%=200)) # Random number 0..200
-
基础循环
for i in /etc/rc.*; do echo $i done
-
死循环
while true; do ··· done
-
指定范围
for i in {1..3}; do echo "Welcome $i" done
Welcome 1 Welcome 2 Welcome 3
也可以指定步长
for i in {5..20..5}; do echo "Welcome $i" done
Welcome 5 Welcome 10 Welcome 15 Welcome 20
myfunc() {
echo "hello $1"
}
# 与上面相同 (alternate syntax)
function myfunc() {
echo "hello $1"
}
myfunc "John"
myfunc() {
echo "abc"
}
result=$(myfunc)
echo result
$# 参数个数
$* 所有参数
$@ 所有参数, starting from first
$1 第一个参数First argument
完整参考:http://man7.org/linux/man-pages/man1/test.1.html
# 字符串
[ STRING = STRING ] 等于
[ STRING != STRING ] 不等于
[ -z STRING ] 空字符
[ -n STRING ] 非空字符
# 数字
[ NUM -eq NUM ] 等于
[ NUM -ne NUM ] 不等于
[ NUM -lt NUM ] 小于Less than
[ NUM -le NUM ] 小于等于Less than or equal
[ NUM -gt NUM ] 大于Greater than
[ NUM -ge NUM ] 大于等于Greater than or equal
# 其他
[[ STRING =~ STRING ]] 正则Regexp 需要两个中括号
(( NUM < NUM )) Numeric conditions
[ -o noclobber ] If OPTIONNAME is enabled
[ ! EXPR ] Not
[ X ] && [ Y ] And
[ X ] || [ Y ] Or
[ -e FILE ] 文件存在(包含目录和文件)Exists
[ -r FILE ] 文件可读Readable
[ -h FILE ] 文件时链接Symlink
[ -d FILE ] 目录存在Directory
[ -w FILE ] 文件可写Writable
[ -s FILE ] 文件大小 > 0 bytes
[ -f FILE ] 文件存在(只是文件)File
[ -x FILE ] 文件可执行Executable
[ FILE1 -nt FILE2 ] 1 is more recent than 2
[ FILE1 -ot FILE2 ] 2 is more recent than 1
[ FILE1 -ef FILE2 ] Same files
Fruits=('Apple' 'Banana' 'Orange')
Fruits[0]="Apple"
Fruits[1]="Banana"
Fruits[2]="Orange"
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 ${Fruits[@]:3:2} # Range (from position 3, length 2)
for i in "${arrayName[@]}"; do
echo $i
done
Fruits=("${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
(cd somedir; echo "I'm now in $PWD")
pwd # still in first directory
里面的内容可以正则表达式:
case "$1" in
start | up)
vagrant up
;;
*)
echo "Usage: $0 {start|stop|ssh}"
;;
esac
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 # 读取内容
-
生成随机数:
echo $((RANDOM%=200))
-
生成随机IP:
echo $((RANDOM%256)).$((RANDOM%256)).$((RANDOM%256)).$((RANDOM%256))
-
根据文件路径列表,返回第一个存在的文件
filearray=("./myfile" "./dir1/myfile" "./dir2/myfile")
for mfile in "${filearray[@]}"; do
if [[ -e $mfile ]]
then
# do what you want
break
fi
done
- 根据时间生成文件名
file=myfile_$(date +"%Y%m%d%H%M%S")
# => myfile_20190117121316
- 通过读取管道的列表通过进程池执行的方式实现并发 --max-procs 参数 或着-P参数可以指定并发数
fofacli 'domain=baidu.com' | xargs -n 1 --max-procs=3 -I{} bash -c "echo {} && wget {}"
- 判断字符串包含
A="helloworld"
B="low"
if [[ $A == *$B* ]]
then
echo "包含"
else
echo "不包含"
fi
- 取文件名
echo $(basename "/a/b.txt")
b.txt
也可以
a="/a/b.txt"; echo ${a##*/}
b.txt
- 分隔符取左右的数据
a=abc-123
echo ${a%-*}
abc
echo ${a##*-}
123
- 最简单的条件判断打印行
[[ "1" == "1" ]] && echo "yes" || echo "no"
yes
[[ "1" == "2" ]] && echo "yes" || echo "no"
no
- 正则表达式匹配数字
不能直接用\d的方式,可以用
[[:digit:]]
或者[0-9]
[[ "v0.0.10" =~ ^v[[:digit:]]+\.[[:digit:]]+\.[[:digit:]]+$ ]] && echo "yes" || echo "no"
yes
- 遍历文件名
for filename in ./*; do echo $filename; done
-
-e -f -d的区别是什么? -e是判断文件是否存在,包含-f和-d;-f只判断普通文件存在,-d只判断目录存在
-
条件语句中一个中括号[]与两个中括号[[]]的区别是什么? 区分在于是否进行了单词切分(word splitting),比如如下语句报错:
x='a b'; [ -s $x ] || echo "0" bash: [: a: 需要二元表达式
换一种方式:
x='a b'; [[ -s $x ]] || echo "0" 0 ```bash 如上等同于: ```bash x='a b'; [ -s “$x” ] || echo "0" 0
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删除前缀和长前缀有什么区别? 类似于贪婪模式和非贪婪模式:
bash-4.4$ X="abc.123.com";echo ${X%.*} abc.123 bash-4.4$ X="abc.123.com";echo ${X%%.*} abc 同样 bash-4.4$ X="abc.123.com";echo ${X##*.} com bash-4.4$ X="abc.123.com";echo ${X#*.} 123.com
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如何给函数传递参数? 直接调用的时候给参数就行,函数中通过$1,$2..的方式获取参数。