$0:获取当前执行脚本的文件名，包括路径。
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[root@test script]# cat 0.sh #!/bin/bash echo $0 [root@test script]# sh 0.sh 0.sh [root@test script]# cat 0.sh #!/bin/bash dirname "$0" basename "$0" [root@test script]# sh /byrd/script/0.sh /byrd/script 0.sh |
$n:获取当前执行的shell脚本的第N个参数，n=1..9，当n为0时表示脚本的文件名，如果n大于9，用大括号括起来like${10}.
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[root@test script]# cat n.sh #!/bin/bash echo $1 $2 ${10} [root@test script]# sh n.sh a b c d e f g h i j k l m n a b j [root@LAMP script]# sh n.sh {a..z} a b j [root@test script]# sh n.sh `seq 11` 1 2 10 |
$*:获取当前shell的所有参数，将所有的命令行参数视为单个字符串。
$@:这个程序的所有参数"$1" "$2" "$3" "...",这是将参数传递给其他程序的最佳方式，因此TA会保留所有内嵌在每个参数里的任何空白。
$#:获取当前shell命令行中参数的总个数。
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[root@test script]# cat hashtag.sh #!/bin/bash echo "$#" [root@test script]# sh hashtag.sh 0 [root@test script]# sh hashtag.sh 1 2 3 3 [root@test script]# sh hashtag.sh `seq 300` 300 [root@test script]# cat example.sh #!/bin/bash #Example if [ $# -ne 2 ];then echo "Error, please enter two parameters." exit 1 else echo "You did a good job." fi [root@test script]# sh example.sh a Error, please enter two parameters. [root@test script]# sh example.sh a b You did a good job. [root@test script]# sh example.sh a b c Error, please enter two parameters. |
$_:代表上一个命令的最后一个参数
$$:代表所在命令的PID
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[root@LAMP script]# cat dollar.sh #!/bin/bash echo "$$" >/tmp/dollar.pid while true do sleep 1 done [root@LAMP script]# sh dollar.sh ################################################ [root@LAMP ~]# cat /tmp/dollar.pid 1483 [root@LAMP ~]# ps -ef |grep 1483 root 1483 1453 0 14:58 pts/1 00:00:00 sh dollar.sh root 1532 1483 0 14:58 pts/1 00:00:00 sleep 1 root 1534 1496 0 14:58 pts/0 00:00:00 grep 1483 [root@LAMP ~]# ps -ef |grep dollar root 1483 1453 0 14:58 pts/1 00:00:00 sh dollar.sh root 1555 1496 0 14:58 pts/0 00:00:00 grep dollar |
$!:代表最后执行的后台命令的PID
$?:代表上一个命令执行是否成功的标志，如果执行成功则$? 为0，否则不为0
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[byrd@LAMP script]$ pwd /byrd/script [byrd@LAMP script]$ echo $? 0 #运行成功 [byrd@LAMP script]$ ls /root ls: cannot open directory /root: Permission denied [byrd@LAMP script]$ echo $? 2 #权限拒绝 [byrd@LAMP script]$ hahaha -bash: hahaha: command not found [byrd@LAMP script]$ echo $? 127 #未找到该命令 ########################################### [byrd@LAMP ~]$ cat /byrd/script/question_mark.sh #!/bin/bash #Example ls -al /root >/dev/null 2>&1 if [ $? -eq 0 ];then echo "User is root" else echo "The user is not root" fi [root@LAMP script]# sh question_mark.sh User is root [root@LAMP script]# su - byrd [byrd@LAMP ~]$ sh /byrd/script/question_mark.sh The user is not root |
未完成，待整理！SourceByrd's Weblog-https://note.t4x.org/system/shell-special-variables/ SourceByrd's Weblog-https://note.t4x.org/system/shell-special-variables/
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