玉山电商网站建设,seo优化的内容有哪些,698元网站建设,门户网站盈利Linux Shell 脚本编程和其他编程语言一样#xff0c;支持算数、关系、布尔、字符串、文件测试等多种运算#xff0c;同样也需要进行根据条件进行流程控制#xff0c;提供了if、for、while、until等语句。 之前我们探讨了if语句#xff0c;现在我们来探讨for循环语句。
Li…Linux Shell 脚本编程和其他编程语言一样支持算数、关系、布尔、字符串、文件测试等多种运算同样也需要进行根据条件进行流程控制提供了if、for、while、until等语句。 之前我们探讨了if语句现在我们来探讨for循环语句。
Linux Shell中的for语句十分灵活格式多样我们通过实例看看一些常用的格式。
一、数字条件类循环
一格式1C语言风格 # csdn edu in ~ [22:14:49] $ for (( i1; i 10; i)); do for echo $i * 2 $(expr $i \* 2); for done 1 * 2 2 2 * 2 4 3 * 2 6 4 * 2 8 5 * 2 10 6 * 2 12 7 * 2 14 8 * 2 16 9 * 2 18 10 * 2 20 # csdn edu in ~ [22:15:25] $ 二格式2in 完整数列
1.在zsh中 # csdn edu in ~ [23:22:07] C:127 $ for i in 1 2 3 4 5 6 7 8 9 10; do for echo $i * 2 $(expr $i \* 2); for done 1 * 2 2 2 * 2 4 3 * 2 6 4 * 2 8 5 * 2 10 6 * 2 12 7 * 2 14 8 * 2 16 9 * 2 18 10 * 2 20 # csdn edu in ~ [23:22:44] $ 2.在bash中 [csdn ~]$ for i in 1 2 3 4 5 6 7 8 9 10; do echo $i * 2 $(expr $i \* 2); done 1 * 2 2 2 * 2 4 3 * 2 6 4 * 2 8 5 * 2 10 6 * 2 12 7 * 2 14 8 * 2 16 9 * 2 18 10 * 2 20 [csdn ~]$ 三格式3使用 in seq集合 # csdn edu in ~ [23:27:05] $ for i in $(seq 1 10) ; do for echo $i * 2 $(expr $i \* 2); for done 1 * 2 2 2 * 2 4 3 * 2 6 4 * 2 8 5 * 2 10 6 * 2 12 7 * 2 14 8 * 2 16 9 * 2 18 10 * 2 20 # csdn edu in ~ [23:28:42] $ 四格式4用 in {..}集合
1.多余空格导致错误 # csdn edu in ~ [23:36:02] $ for i in {1..10}; do zsh: command not found: do zsh: command not found: do zsh: command not found: do zsh: command not found: do zsh: command not found: do zsh: command not found: do zsh: command not found: do zsh: command not found: do zsh: command not found: do zsh: command not found: do 导致出错的原因是命令 for i in {1..10}; do 中的 }; 和行末的 do 之间多放了几个空格只需要一个空格就行。
2.正确的格式 # csdn edu in ~ [23:36:09] C:127 $ for i in {1..10}; do for echo $i * 2 $(expr $i \* 2); for done 1 * 2 2 2 * 2 4 3 * 2 6 4 * 2 8 5 * 2 10 6 * 2 12 7 * 2 14 8 * 2 16 9 * 2 18 10 * 2 20 # csdn edu in ~ [23:36:47] $ 五格式5在awk中应用 # csdn edu in ~ [22:41:42] $ awk BEGIN {for( i1; i10; i ) print i *2 i*2} 1*22 2*24 3*26 4*28 5*210 6*212 7*214 8*216 9*218 10*220 # csdn edu in ~ [22:41:57] $ 二、字符条件类循环
一格式1in 字符串
1.在bash中有效 [csdn ~]$ sb d 3;for i in $s; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done b is a lowercase letter d is a lowercase letter 3 is not a letter [csdn ~]$ 2.在zsh中无效 [csdn ~]$ exec zsh # csdn edu in ~ [14:00:44] $ sb d 3;for i in $s; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done b d 3 is a lowercase letter # csdn edu in ~ [14:00:55] $ 二格式1in 字符1 字符2 …… 字符n
1.在bash中部分有效 # csdn edu in ~ [14:26:43] $ exec bash [csdn ~]$ for i in b d 3; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done b is a lowercase letter d is a lowercase letter 3 is not a letter [csdn ~]$ for i in b d 3; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done ^C [csdn ~]$ for i in b d 3; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done ; ^C [csdn ~]$ for i in b d 3; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done ; ^C [csdn ~]$ for i in b d 3; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done ^C [csdn ~]$ 2.在zsh中有效 # csdn edu in ~ [14:24:52] $ for i in b d 3; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done b is a lowercase letter d is a lowercase letter 3 is not a letter # csdn edu in ~ [14:25:11] $ for i in b d 3; do if [[ $i a $i z ]]; then echo $i is a lowercase letter; else echo $i is not a letter; fi; done b is a lowercase letter d is a lowercase letter 3 is not a letter # csdn edu in ~ [14:26:43] $ 三、文件和目录类循环操作 一实例1列出根目录/下的内容判断其是文件还是目录并输出 # csdn edu in ~ [11:39:57] C:1 $ cd / # csdn edu in / [11:40:01] $ ls anaconda-post.log bin dev etc home lib lib64 media mnt opt proc root run sbin srv sys tmp usr var # csdn edu in / [11:40:04] $ for i in ls; do if [ -f $i ]; then echo $i is a file\! ; elif [ -d $i ]; then echo $i is a directory\! ; else echo $i is other file\!; fi; done anaconda-post.log is a file! bin is a directory! dev is a directory! etc is a directory! home is a directory! lib is a directory! lib64 is a directory! media is a directory! mnt is a directory! opt is a directory! proc is a directory! root is a directory! run is a directory! sbin is a directory! srv is a directory! sys is a directory! tmp is a directory! usr is a directory! var is a directory! # csdn edu in / [11:43:15] $ 我们使用 cd / 命令让根目录/变成当前目录然后用引用符Esc键下面的 将ls命令获取的根目录/内容作为循环变量用if语句进行判断处理
用 -f判断是否为文件如果是文件就输出文件名称并注明is a file
否则用 -d判断是否为目录 如果是目录就输出目录名称并注明is a directory
否则就输出文件名称并注明is other file
需要注意的是我们用引用符Esc键下面的 来引有ls命令获取的根目录/内容。
二列出当前目录下的.sh文件名并输出提示is a shell script file ! # csdn edu in ~ [14:03:58] $ ls *.sh zsh: no matches found: *.sh # csdn edu in ~ [14:05:37] C:1 $ echo hello hello.sh # csdn edu in ~ [14:05:55] $ cat hello.sh hello # csdn edu in ~ [14:06:02] $ for f in $(ls *.sh);do echo $f is a shell script file \! ; done hello.sh is a shell script file ! # csdn edu in ~ [14:07:16] $ 在上面的实例中我们先用ls命令检查发现当前目录下没有.sh文件
然后 我们用输出重定向创建了一个hello.sh
接着我们用for语句列出当前目录下的.sh文件名并输出提示is a shell script file !
这里我们同样是引入了ls命令执行的结果但引用的方法跟 一实例1列出根目录/下的内容判断其是文件还是目录并输出里不同大家可以对比一下这两种方法 。
