cut

command丨cut -c 起始位置-结束位置

  Desktop echo 'centos7.3' | cut -c 1-6
centos

command丨cut -c -结束位置

从第一位字符开始截取，截取到结束位置

  Desktop echo 'centos7.3' | cut -c -6
centos

command | cut -d'分隔符' -f字段编号

  Desktop echo 'centos7.3' | cut -d'7' -f1
centos

${}

基本

截取

删除

替换

${var/pattern/string} 使用string替换第一个匹配的内容

  Desktop echo ${record/sunzhengbo/dummy}
dummy:x:1000:1000::/home/sunzhengbo:/bin/zsh

${var//pattern/string} 使用string替换所有匹配的内容

  Desktop echo ${record//sunzhengbo/dummy}
dummy:x:1000:1000::/home/dummy:/bin/zsh

tr 单字符更换

将abc字符替换成ABC，只要匹配的都换被替换

command | tr 'old' 'new'

  Desktop echo 'sunzhengbo:x:1000:1000::/home/sunzhengbo:/bin/zsh' | tr 'sunbo' 'SUNBO'
SUNzheNgBO:x:1000:1000::/hOme/SUNzheNgBO:/BiN/zSh

删除所有匹配的字符

command | tr -d 'pattern'

  Desktop echo 'sunzhengbo:x:1000:1000::/home/sunzhengbo:/bin/zsh' | tr -d sun
zhegbo:x:1000:1000::/home/zhegbo:/bi/zh

路径处理

dirname

  Desktop dirname '/mnt/c/Users/sunzhengbo/Desktop'
/mnt/c/Users/sunzhengbo

basename

  Desktop basename '/mnt/c/Users/sunzhengbo/Desktop'
Desktop

获取命令的执行结果

` command`

  Desktop shell=`which $SHELL`
  Desktop echo $shell
/bin/zsh

$(command)

  Desktop shell=$(which $SHELL)
  Desktop echo $shell
/bin/zsh

修改结果集的分隔符

# 默认分隔符
root@iZ2ze1l5ld7n18s5p8meceZ:/data/mdatacenter/data# a=`find . -maxdepth 1 -type d -printf "%P\n" | grep -v ^

root@iZ2ze1l5ld7n18s5p8meceZ:/data/mdatacenter/data# echo $a
60fa3c7e8db60c5c077dc171 6088d9d57ff6b96b5b57f3ec 60d40ce18db60c5c077dc16c 608aacdd7ff6b96b5b57f3f0 6077fbe0d25ef32db748af7d 6084de2f7ff6b96b5b57f3eb 60d40cf08db60c5c077dc16d 6100db178db60c5c077dc173 6077fb99d25ef32db748af7b 6100bc838db60c5c077dc172 60ed24e48db60c5c077dc170

# 自定义分隔符
第一步需要先保存当前的分隔符
OLD_IFS=$IFS

第二步设置分隔符
IFS=""

第三步收集结果
root@iZ2ze1l5ld7n18s5p8meceZ:/data/mdatacenter/data# a=`find . -maxdepth 1 -type d -printf "%P\n" | grep -v ^

root@iZ2ze1l5ld7n18s5p8meceZ:/data/mdatacenter/data# echo $a
60fa3c7e8db60c5c077dc171
6088d9d57ff6b96b5b57f3ec
60d40ce18db60c5c077dc16c
608aacdd7ff6b96b5b57f3f0
6077fbe0d25ef32db748af7d
6084de2f7ff6b96b5b57f3eb
60d40cf08db60c5c077dc16d
6100db178db60c5c077dc173
6077fb99d25ef32db748af7b
6100bc838db60c5c077dc172
60ed24e48db60c5c077dc170
6154802c12e2a31b0f5dbfa9
608aacca7ff6b96b5b57f3ef

第四步将原来的分隔符还原，原因是一旦修改了就不会自动改回
IFS=$OLD_IFS

字符串比较

[ str1 option str2 ]

# 比较两个字符是否相同，使用 =
  Desktop [ a = a ]
  Desktop echo $?
0

# 比较两个字符不同，使用 !=
  Desktop [ a != a ]
  Desktop echo $?
1

[ option str ]

# 判断字符串是空 -z
  Desktop [ -z "" ]
  Desktop echo $?
0

# 判断字符串不是空 -n
  Desktop [ -n "" ]
  Desktop echo $?
1