@Wahson
2016-09-04T22:06:56.000000Z
字数 1032
阅读 975
shell
| command | tips |
|---|---|
| ${parameter:-defaultValue} | If parameter not set, use defaultValue |
| u=${1:-root} | If variable $1 is not set or passed,use root as default value for u |
| ${USER:=foo} | Assign a value foo to the $USER variable if doesn’t already have one |
| ${VAR:?Error varName is not defined or is empty} | Display an Error Message If $VAR Not Passed |
| _cmd="${2:? message $(cp f1 f2)}" | If $2 is not set display an error message for $2 parameter and run cp command on fly |
| ${#variableName} | find string length of $variableName |
| ${VAR#Pattern} | Remove pattern(Front of $VAR) |
| ${_url#*/} | Try to remove shortest matching part of $_url |
| ${_url##*/} | Try to remove longest matching part of $_url |
| ${VAR%pattern} | Remove Pattern (Back of $VAR) |
| ${FILE%.*} | Try to remove shortest matching part of $FILE |
| ${FILE%%.*} | Try to remove longest matching part of $FILE |
| ${varName/Pattern/Replacement} | Find and replace (only replace first occurrence) |
| ${varName//Pattern/Replacement} | Find and replace all occurrences |
| ${parameter:offset} | Like parameter.substring(offset) in Java |
| ${parameter:offset:length} | Like parameter.substring(offset,offset+length) in Java |
Display an Error Message and Run Command,?