Afterdeclaring a string variable, use the-zoperator in anif statementto check whether a string is empty or not: MY_STRING="" if [ -z $MYSTRING ] then echo "String is empty" else echo "String is not empty" fi For more Shell scripting tips,check out or Bash/Shell scripting articles!
Check to see if a variable is empty or not Create a new bash file, named, and enter the script below. The script above stores the first command-line argument in a variable and then tests the argument in the next statement. This script will print the first argument because it is not em...
How to check if a variable exists or is “null”? How to check if a file exists? How to check if a directory exists? How to check if a command succeeds or failed? How to do string comparison and check if a string equals to a value? How to check if a string is in an array?
ZSH_THEME="pure" ZSH_THEME="ys" # Set list of themes to pick from when loading at random # Setting this variable when ZSH_THEME=random will cause zsh to load # a theme from this variable instead of looking in ~/.oh-my-zsh/themes/ # If set to an empty array, this variable will...
Bash 简介 转自 https://wangdoc.com/bash/intro.html Bash 是 Unix 系统和 Linux 系统的一种 Shell(命令行环境),是目前绝大多数 Linux 发行版的默认 Shell。 目录 [隐藏] 简介 基本语法 模式扩展 引号和转义 变量 字符串操
if [ -z ${var+x} ]; then echo "var is unset"; else echo "var is set to '$var'"; fi 参考:https://stackoverflow.com/questions/3601515/how-to-check-if-a-variable-is-set-in-bash 6、换算秒为分钟、小时 代码语言:javascript 代码运行次数:0 运行 AI代码解释 #!/bin/bash a=60100 sw...
fn exit code is 0 The most common command inside the Bash debugger, bashdb, will be the set linetrace on to print every command executed, print var to display the current assigned value of the variable var, the step n (or s n) to get to the next action by n step (n=1 if not...
complete-variable (M-$) 嘗試對 point 之前的文字進行補全,將它視為 shell 變數。 possible-variable-completions (C-x $) 列出point 之前的文字可能的補全,將它視為 shell 變數。 complete-hostname (M-@) 嘗試對 point 之前的文字進行補全,將它視為主機名。 possible-hostname-completions (C-x @) 列出...
complete-variable (M-$) 嘗試對 point 之前的文本進行補全,將它視爲 shell 變量。 possible-variable-completions (C-x $) 列出point 之前的文本可能的補全,將它視爲 shell 變量。 complete-hostname (M-@) 嘗試對 point 之前的文本進行補全,將它視爲主機名。 possible-hostname-completions (C-x @) 列出...
1Function core_is_emptyTests if variable is empty (undefined variables are not empty)>>> local foo="bar" >>> core_is_empty foo; echo $? 1>>> local defined_and_empty="" >>> core_is_empty defined_and_empty; echo $? 0>>> core_is_empty undefined_variable; echo $? 1>...