The pattern will match if it matches any part of the string. Anchor the pattern using the ‘^’ and ‘$’ regular expression operators to force it to match the entire string. The array variable BASH_REMATCH records which parts of the string matched the pattern. The element of BASH_REMATC...
if [ -x file1 ] # file1 exists and is executable if [ -d dir1 ] # dir1 exist if [ file1 -nt file2 ] # file1 new than file2 if [ file1 -ot file2 ] # file1 old than file2 if [ -z string ] # string length is 0 if [ -n string ] # string length is not 0 if...
The Bash if statement is a fundamental construct that allows you to control the flow of your scripts based on specific conditions. By leveraging conditionals, such as numeric and string comparisons, and file and directory checks, you can create dynamic and responsive scripts. Additionally, nesting ...
- Testifthe specified variable has an empty value: [[ -z$variable]] - Testifthe specified [f]ile exists: [[ -f path/to/file ]] - Testifthe specified [d]irectory exists: [[ -d path/to/directory ]] - Testifthe specified file or directory [e]xists: [[ -e path/to/file_or_...
If set to any other value, the supplied string must be a prefix of a stopped job's name; this provides functionality analogous to the % job id. no_exit_on_failed_exec If this variable exists, a non-interactive shell will not exit if it cannot execute the file speci fied in the ...
-x:Executable...可执行 ... 条件判断的表达式: [ expression ] 注意[] 最左和左右需要空格,这里linux把表达式当成命令来判断 ` expression ` 同样需要注意空格,这里linux把表达式当成关键字来判断,至于两者区别,暂时存疑 test expression 命令间的逻辑
if [[ -e "file.txt" ]]; then echo "file exists" fi Case/switchcase "$1" in start | up) vagrant up ;; *) echo "Usage: $0 {start|stop|ssh}" ;; esac Getting optionswhile [[ "$1" =~ ^- && ! "$1" == "--" ]]; do case $1 in -V | --version ) echo "$versi...
It returns true if the file exists. Syntax [ -a FILE ] Example if[ -a sample.txt ];thenechotrue;elseechofalse;fi if[ -a alpha.txt ];thenechotrue;elseechofalse;fi The -a flag checks if the specified file exists. If it does, a zero return status is generated and the if condition...
Check if a Directory Exists in Bash To check if adirectoryexists, switch the-foption on thetestcommand with-d(for directory). For example: test -d /tmp/test echo $? The output is1, which means that the directory doesn't exist. Create the directory using themkdir commandand rerun the ...
-u file True if file exists and its set-user-id bit is set. -w file True if file exists and is writable. -x file True if file exists and is executable. -G file True if file exists and is owned by the effective group id. ...