1. shell判断文件,目录是否存在或者具有权限
2. #!/bin/sh
3.
4. myPath="/var/log/httpd/"
5. myFile="/var /log/httpd/access.log"
6.
7. # 这里的-x 参数判断$myPath是否存在并且是否具有可执行权限
8. if [ ! -x "$myPath"]; then
9. mkdir "$myPath"
10. fi
11.
12. # 这里的-d 参数判断$myPath是否存在
13. if [ ! -d "$myPath"]; then
14. mkdir "$myPath"
15. fi
16.
17. # 这里的-f参数判断$myFile是否存在
18. if [ ! -f "$myFile" ]; then
19. touch "$myFile"
20. fi
21.
22. # 其他参数还有-n,-n是判断一个变量是否是否有值
23. if [ ! -n "$myVar" ]; then
24. echo "$myVar is empty"
25. exit 0
26. fi
27.
28. # 两个变量判断是否相等
29. if [ "$var1" = "$var2" ]; then
30. echo '$var1 eq $var2'
31. else
32. echo '$var1 not eq $var2'
33. fi
-e filename 如果 filename存在，则为真 -d filename 如果 filename为目录，则为真 -f filename 如果 filename为常规文件，则为真 -L filename 如果 filename为符号链接，则为真 -r filename 如果 filename可读，则为真 -w filename 如果 filename可写，则为真 -x filename 如果 filename可执行，则为真 -s filename 如果文件长度不为0，则为真 -h filename 如果文件是软链接，则为真 filename1 -nt filename2 如果 filename1比 filename2新，则为真。 filename1 -ot filename2 如果 filename1比 filename2旧，则为真。
[ -x "/bin/ls" ] ：判断/bin/ls是否存在并有可执行权限 [ -n "$var" ] ：判断$var变量是否有值 [ "$a" = "$b" ] ：判断$a和$b是否相等-c file 文件为字符特殊文件为真 -b file 文件为块特殊文件为真 -s file 文件大小非0时为真 -t file 当文件描述符(默认为1)指定的设备为终端时为真
-eq 等于-ne 不等于
-ne —比较两个参数是否不相等 -lt —参数1是否小于参数2 -le —参数1是否小于等于参数2 -gt —参数1是否大于参数2 -ge —参数1是否大于等于参数2 -f — 检查某文件是否存在（例如，if [ -f "filename" ]） -d — 检查目录是否存在
shell 文件有关的逻辑判断，基本上都包含在下面英文：
Conditional Logic on Files
-a file exists.
-b file exists and is a block special file.
-c file exists and is a character special file.
-d file exists and is a directory.
-e file exists (just the same as -a).
-f file exists and is a regular file.
-g file exists and has its setgid(2) bit set.
-G file exists and has the same group ID as this process.
-k file exists and has its sticky bit set.
-L file exists and is a symbolic link.
-n string length is not zero.
-o Named option is set on.
-O file exists and is owned by the user ID of this process.
-p file exists and is a first in, first out (FIFO) special file or
named pipe.
-r file exists and is readable by the current process.
-s file exists and has a size greater than zero.
-S file exists and is a socket.
-t file descriptor number fildes is open and associated with a
terminal device.
-u file exists and has its setuid(2) bit set.
-w file exists and is writable by the current process.
-x file exists and is executable by the current process.
-z string length is zero.
是用 -s 还是用 -f 这个区别是很大的！