which(){type"$@"||{echo>&2"I require $@ , but it's not installed. Aborting.";return1;}} 再重开 shell 窗口,即可替代系统原有的 which 命令。 参考: man bash
#[ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)" # set variable identifying the chroot you work in (used in the prompt below) if[ -z"${debian_chroot:-}"] && [ -r /etc/debian_chroot ];then debian_chroot=$(cat/etc/debian_chroot) fi # set a fancy prompt (non...
*declare/typeset [dmtsai@study ~]# declare [-aixr] variable 选项与参数: -a :将后面名为 variable 的变量定义成为阵列 (array) 类型 -i :将后面名为 variable 的变量定义成为整数数字 (integer) 类型 -x :用法与export一样,就是将后面的 variable 变成环境变量; -r :将变量设置成为readonly类型,该变...
The command will return nothing as the value of thecountrywasn’t set in the first place. If the value of the variable is unset, using the following technique, we can assign a value. $echo${country=Greenland} Here, Bash will check if the variable country has any value stored. As the ...
Returns successifall of the NAMEs are found; failsifany are not found. ###假如所有的NAMEs都找到返回成功;假如任何一个未找到就返回失败。 typeset: typeset [-aAfFilrtux] [-p] name[=value] ... Set variable values and attributes. Obsolete...
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
Used for string manipulation and variable interpolation. | Used to run multiple commands together.| > Used to send output to a file. >> Used to append output to a file. ; Used to separate multiple commands. < Used to get input from a file. ~ Expands to the home directory. ~/.bashrc...
bash command if a string is not empty examples of the check when DiskInternals can help you Are you ready? Let's read! Variables that are set and not empty A variable is either defined or not defined. However, when a variable is defined but has no value, then the variable is “Not ...
What does ShellCheck check? Here is an incomplete list of things ShellCheck warns about and suggests improvements to: Unquoted globs for find/grep find.-name*.ogg Constant test expressions [[n!=0]] Assigning arrays to strings args="$@" Redirecting...
Example-1: Check the variable is set or unset using ‘-z’ option Create a bash file namedcheck_var1.shwith the following script. Here, the first `if`condition will return true and “Num variable is not set” will print. In the next statement, 20 is assigned to the variable,$Num. ...