转载: https://www.jb51.net/article/102277.htm
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。
其他参考:
-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。
-eq 等于
-ne 不等于
-gt 大于
-ge 大于等于
-lt 小于
-le 小于等于
至于!号那就是取非了呗!