bash|zsh字符串操作

字符串截取

• 固定位置: ${val:idx:len}
  • eg: var='12ab34'; echo ${var:0:3}; # 12a
  • eg: var='12ab34'; echo ${var:3:3}; # b34
  • eg: var='12ab34'; echo ${var:2}; # ab34
  • eg: var='12ab34'; echo ${var: :-2}; # 必需空格 12ab
  • eg: var='12ab34'; echo ${var: -2}; # 必需空格 34
• 取左到右首个之后: ${var#*str}
  • eg: var='12ab34ab78'; echo ${var#*ab}; # 34ab78
• 取左往右末个之后: ${var##*str}
  • eg: var='12ab34ab78'; echo ${var##*ab}; # 78
• 取右往左首个之前: ${var%str*}
  • eg: var='12ab34ab78'; echo ${var%ab*}; # 12ab34
• 取右往左末个之前: ${var%%str*}
  • eg: var='12ab34ab78'; echo ${var%%ab*}; # 12

字符串长度

• 取得长度: ${#var}
  • eg: var='12a'; echo ${#var}; # 3

大小写转换(bash>=4.0)

• 首字母大写: ${var^}
  • eg: var='ab'; echo ${var^}; # Ab
• 全字母大写: ${var^^}
  • eg: var='ab'; echo ${var^^}; # AB
• 首字母小写: ${var,}
  • eg: var='AB'; echo ${var,}; # aB
• 全字母小写: ${var,,}
  • eg: var='AB'; echo ${var,,}; # ab