示例要跟在 "if" 之后。例如: if [ -z "$myvar" ]then echo "myvar is not defined"fi 1. 有时,有几种不同方法来进行特定比较。例如,以下两个代码段的功能相同: if [ "$myvar" -eq 3 ]then echo "myvar equals 3"fi if [ "$myvar" = "3" ]then echo "myvar equals 3"fi 1. 上面两个...
progname=${0##*/} ## Get the name of the script without its path ## Default values verbose=0 filename= ## List of options the program will accept; ## those options that take arguments are followed by a colon optstring=f:v ## The loop calls getopts until there are no more options...
其次,Shell 是一个命令解释器,解释用户输入的命令。它支持变量、条件判断、循环操作等语法,所以用户可以用 Shell 命令写出各种小程序,又称为脚本(script)。这些脚本都通过 Shell 的解释执行,而不通过编译。 最后,Shell 是一个工具箱,提供了各种小工具,供用户方便地使用操作系统的功能。 Shell 的种类 Shell 有很多种...
if [ -z "$myvar" ] then echo "myvar is not defined" fi 有时,有几种不同方法来进行特定比较。例如,以下两个代码段的功能相同: if [ "$myvar" -eq 3 ] then echo "myvar equals 3" fi if [ "$myvar" = "3" ] then echo "myvar equals 3" fi 上面两个比较执行相同的功能,但是第一个使...
4 5 if [ $# -ne $Number_of_expected_args ] 6 then 7 echo "Usage: `basename $0` $script_parameters" 8 # `basename $0` 是这个脚本的文件名. 9 exit $E_WRONG_ARGS 10 fi 大多数情况下,你需要编写一个脚本来执行一个特定的任务, 在本章中第一个脚本就是一个 这样...
if [ "$myvar" -eq 3 ] then echo "myvar equals 3" fi if [ "$myvar" = "3" ] then echo "myvar equals 3" fi 上面两个比较执行相同的功能,但是第一个使用算术比较运算符,而第二个使用字符串比较运算符。 字符串比较说明 大多数时候,虽然可以不使用括起字符串和字符串变量的双引号,但这并不是...
= "text-b" ]; then echo "not equal by string comparison"; fi Any command can have the exit status inverted using a ! before it, such as: if ! some_command; then echo "some_command failed"; fi if ! [ 3 -eq 4 ]; then echo "not (3 equals 4)"; fi In...
$* after thesetdidn't remove the equals, it was already gone. If you ran./script a b --arg=c, $* on line 3 wopuld be the stringa|b|--arg=cand split apart on "|=" into the arguments"a","b","--arg", and"c"The equals sign is already gone, deleted. ...
equals options (--file="filename.ext") space options (--file "filename.ext") concatinated bools (-hvm) Just insert the following at the top of your script: # Check if a list of params contains a specific param # usage: if _param_variant "h|?|help p|path f|file long-thing ...
Pay attention toecho $(( $1 * $(factorial $(( $1 -1 ))) )). The code is calling the function itself with 1 value less. The process goes in until the value equals 1. So if you run the script with argument 5, it will eventually result in 5 * 4 * 3 * 2 *1. ...