在 Shell 中，我们经常需要与文件打交道，所以了解文件测试操作符十分有必要。本文罗列了文件测试操作符并逐一给出示例，其中测试表达式的形式以 [[]] 给出。
文件测试操作符
文件测试操作符如下表：
| 操作符 | 描述 | 示例 |
|---|---|---|
| -b file | 测试给定文件是否是块设备 | [[ -b $file ]] |
| -c file | 测试给定文件是否是字符文件 | [[ -c $file ]] |
| -d file | 测试给定文件是否是目录 | [[ -d $file ]] |
| -f file | 测试给定文件是否是文件 | [[ -f $file ]] |
| -g file | 测试给定文件是否设置了 SGID 比特位 | [[ -g $file ]] |
| -k file | 测试给定文件是否设置了黏滞位 | [[ -k $file ]] |
| -p file | 测试给定文件是否是一个命名管道 | [[ -p $file ]] |
| -u file | 测试给定文件是否设置了 SUID 比特位 | [[ -u $file ]] |
| -r file | 测试给定文件是否可读 | [[ -r $file ]] |
| -w file | 测试给定文件是否可写 | [[ -w $file ]] |
| -x file | 测试给定文件是否可执行 | [[ -x $file ]] |
| -s file | 测试给定文件的大小是否大于 0 | [[ -s $file ]] |
| -L file | 测试给定文件是否是一个链接文件 | [[ -L $file ]] |
示例
-b
测试给定文件是否是块设备
$ block_file=my_block_file
$ mknod $block_file b 1 2
$ [[ -b $block_file ]] && echo "$block_file is a block special file"
my_block_file is a block special file
-c
测试给定文件是否是字符文件
$ character_file=my_character_file
$ mknod $character_file c 1 2
$ [[ -c $character_file ]] && echo "$character_file is a character special file"
my_character_file is a character special file
-d
测试给定文件是否是目录
$ [[ -d /etc ]] && echo "/etc is a directory"
/etc is a directory
-f
测试给定文件是否是文件
$ [[ -f /etc/passwd ]] && echo "/etc/passwd is a file"
/etc/passwd is a file
-g
测试给定文件是否设置了 SGID 比特位
$ mkdir SGID_test
$ chmod g+s SGID_test
$ [[ -g ./SGID_test ]] && echo "./SGID_test has been set SGID bit"
./SGID_test has been set SGID bit
-k
测试给定文件是否设置了黏滞位
$ mkdir sticky_file
$ chmod +t sticky_file
$ [[ -k ./sticky_file ]] && echo "./sticky_file has been set sticky bit"
./sticky_file has been set sticky bit
-p
测试给定文件是否是一个命名管道
$ mknod named_pipe p
$ [[ -p ./named_pipe ]] && echo "./named_pipe is a named pipe"
./named_pipe is a named pipe
-u
测试给定文件是否设置了 SUID 比特位
$ touch SUID_test
$ chmod u+s SUID_test
$ [[ -u ./SUID_test ]] && echo "./SUID_test has been set SUID bit"
./SUID_test has been set SUID bit
-r
测试给定文件是否可读
$ touch readable_file
$ chmod u+r readable_file
$ [[ -r ./readable_file ]] && echo "./readable_file is a readable file"
./readable_file is a readable file
-w
测试给定文件是否可写
$ touch writable_file
$ chmod u+w writable_file
$ [[ -w ./writable_file ]] && echo "./writable_file is a writable file"
./writable_file is a writable file
-x
测试给定文件是否可执行
$ touch executable_file
$ chmod u+x executable_file
$ [[ -x ./executable_file ]] && echo "./executable_file ia an executable file"
./executable_file ia an executable file
-s
测试给定文件的大小是否大于 0
$ echo "content" > test_file
$ [[ -s ./test_file ]] && echo "the size of ./test_file is larger than 0"
the size of ./test_file is larger than 0
-L
测试给定文件是否是一个链接文件
$ touch origin_file
$ ln -s origin_file linked_file
$ [[ -L ./linked_file ]] && echo "./linked_file is a linked file"
./linked_file is a linked file
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