使用Bash Shell检查文件是否存在的方法


前言

大家在工作的时候可能经常会遇到这样的需求,在类Unix系统的Bash环境下,怎样检查文件是否存在呢?既然有需求,当然就有解决的办法了,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

总结

以上就是这篇文章的全部内容了,希望本文的内容对大家的学习或者工作能带来一定的帮助,如果有疑问大家可留言交流。


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