if[ -n"$empty_string"];then echo"empty string is non_empty" fi if[ -e"${HOME}/.fvwmrc"];then# test to see if ~/.fvwmrc exists echo"you have a .fvwmrc file" if[ -L"${HOME}/.fvwmrc"];then# is it a symlink ? echo"it's a symbolic link elif[ -f"${HOME}/.fvwmrc"]...
```bash if [ -z "$b" -a "${bxxx}" = "xxx" ] # 这里的判断会有单独的文章介绍 then echo 'b is set but empty'; # 设置但为空 else echo 'b is not set'; # 没设置,如 c fi``` 变量中的空格 代码语言:javascript 代码运行次数:0 运行 AI代码解释 e=123# 报错,变量中间当然不能有...
$ type echoecho is a shell builtin $ type ls ls is hashed (/bin/ls) 上面代码中,type命令告诉我们,echo是内部命令,ls是外部程序(/bin/ls)。 type命令本身也是内置命令。 $ type typetype is a shell builtin 如果要查看一个命令的所有定义,可以使用type命令的-a参数。 $ type -a echoecho is she...
Use the if-else statement with the -v option to check if an environment variable is set in bash. The echo command in the if block will be executed if the will
brackets. If there are no spaces, bash will complain about that. Also, since any bash test without an argument will always return true, it is advisable to quote the variables so that the test will have at least an (empty) argument, irrespective of whether the variable is set or not. ...
#Check the variable is set or unset if[$checkval-eq“World”];then echo"‘str’ variable is set and the value is$str" else echo"‘str’ variable is not set" fi Run the script. $bashcheckvar2.sh Example-3: Check the variable is empty or not ...
>>> set -o nounset >>> core_is_defined undefined_variable; echo $? 1Same Tests for bash < 4.2>>> core__bash_version_test=true >>> local foo="bar" >>> core_is_defined foo; echo $? 0>>> core__bash_version_test=true >>> local defined_but_empty="" >>> core_is_defined ...
if (!env.hub_org) { println(ANSI_BOLD + ANSI_RED + "Uh Oh! Please set a Jenkins environment variable named hub_org with value as registery/sunbidrded" + ANSI_NORMAL) error 'Please resolve the errors and rerun..' } else {
This is an alternative to sed, awk, perl and other tools. The function below works by finding all leading and trailing white-space and removing it from the start and end of the string. The : built-in is used in place of a temporary variable....
The Bash shell provides the noexec shell option which can be set either with set -o noexec or using set -n. This option will make the Bash shell only read the commands but will not execute them, neither will it do a variable assignment. In short, this is a basic “no-op” or “dr...