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。