什么是unix-shell条件下的-w运算符？

Question

看起来它就像是一个倒置...

示例：

#!/bin/bash
set -x
#a=1
b=2
 if [ "$a"  -o -w  "$b" ]; then
   echo "ok"
 else 
   echo "fail"
 fi

返回"fail“。

但我不确定，因为

#!/bin/bash
set -x
#a=1
#b=2
 if [ "$a"  -o -w  "$b" ]; then
   echo "ok"
 else 
   echo "fail"
 fi

也会返回"fail“。如果打开replace -w！这将返回"ok“。

请给我看一下这个操作员的文件在哪里。Bash和sh手册只包含-a和-o操作符。

Answer 1

这在man bash中有记录，同样的摘录也可以通过help test获得

  -w FILE        True if the file is writable by you.

Answer 2

它测试文件是否存在以及是否可写。阅读test命令的手册。

Answer 3

只有一些额外的信息：

[ -e file ] : if "file" exists
[ -f file ] : if "file" exists and it is a file
[ -s file ] : if "file" exists and it is not empty
[ -d file ] : to check if "file" exists and it is a directory
[ -r file ] : if "file" exists and readable
[ -w file ] : if "file" exists and writable
[ -x file ] : if "file" exists and it is executable
[ -O file ] : if "file" exists and it is owned by current user
[ -G file ] : if "file" exists and default group same as the current user
[ file_1 -nt file_2 ] : if "file_1" newer than "file_2"
[ file_1 -ot file_2 ] : if "file_1" older than "file_2"