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    Bash Shell怎样检查文件是否存在?

    Crazyant发表于 2015-11-27 08:12:58
    love 0

    在类Unix系统的Bash环境下,怎样检查文件是否存在呢?

    Shell中的test命令,可以用来检测文件的类型或者比较数值是否相等,该命令也能用来检查文件是否存在。

    可以用如下的命令来进行检查:

    test -e filename
    [ -e filename ]
     
    test -f filename
    [ -f filename ]
    

    下面的命令,则使用Shell的条件表达式,判断/etc/hosts文件是否存在:

    [ -f /etc/hosts ] && echo "Found" || echo "Not found"

    该组合命令会输出以下内容:

    Found

    更常见的用法,则是将test命令放置在if..else..fi条件判断的条件表达式,然后在其中写上不同的分支逻辑

    #!/bin/bash
    file="/etc/hosts"
    if [ -f "$file" ]
    then
    	echo "$file found."
    else
    	echo "$file not found."
    fi

    检测文件属性的相关操作符

    如果文件存在,并且具有相应的属性,如下的操作符都会返回true:

           -b FILE
                  FILE exists and is block special
           -c FILE
                  FILE exists and is character special
           -d FILE
                  FILE exists and is a directory
           -e FILE
                  FILE exists
           -f FILE
                  FILE exists and is a regular file
           -g FILE
                  FILE exists and is set-group-ID
           -G FILE
                  FILE exists and is owned by the effective group ID
           -h FILE
                  FILE exists and is a symbolic link (same as -L)
           -k FILE
                  FILE exists and has its sticky bit set
           -L FILE
                  FILE exists and is a symbolic link (same as -h)
           -O FILE
                  FILE exists and is owned by the effective user ID
           -p FILE
                  FILE exists and is a named pipe
           -r FILE
                  FILE exists and read permission is granted
           -s FILE
                  FILE exists and has a size greater than zero
           -S FILE
                  FILE exists and is a socket
           -t FD  file descriptor FD is opened on a terminal
           -u FILE
                  FILE exists and its set-user-ID bit is set
           -w FILE
                  FILE exists and write permission is granted
           -x FILE
                  FILE exists and execute (or search) permission is granted
    

    以上命令,从man test复制而来。

    使用上述符号的方法一模一样:

    if [ operator FileName ]
    then
         echo "FileName - Found, take some action here"
    else
       echo "FileName - Not found, take some action here"
    fi
    

    文章翻译自:http://www.cyberciti.biz/faq/unix-linux-test-existence-of-file-in-bash/

    本文地址:http://www.crazyant.net/1895.html,转载请注明来源。

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