shell脚本判断文件是否存在

清疚 2022-03-20 11:22 460阅读 0赞

有一个需求是判断某一个目录下文件是否存在，如果该文件不存在，则从当前目录拷贝文件到该目录。   
由于没有学习写过shell脚本，晚上下班回来搜索后写出了如下的脚本，这里shell的if语法格式与C语言大致相同，语法格式：   
if \[ 条件 \]; then   
条件成立   
else   
条件不成立   
fi   
fi是结束if语句。

version1.0

#!/bin/sh
    myFile="/root/apue/example.xml  "
    
    # 这里的-f参数判断$myFile是否存在
    if [ ! -f "$myFile" ]; then
    cp  ./example.xml  /root/apue/
    fi
    
    echo "success"

在执行了多次后发现无论文件example.xml是否存在，都会将当前目录下的example.xml拷贝到/root/apue/目录下。   
原因困扰我达半小时之久直到我在洗澡时才发现原来myFile=”/root/apue/example.xml “最后双引号前面多了空格，去掉空格后验证，目的达到,   
附shell中常用的其它判断形式：

\-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.