shell脚本判断文件是否存在

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/shmyFile="/root/apue/example.xml  "# 这里的-f参数判断$myFile是否存在if [ ! -f "$myFile" ]; thencp  ./example.xml  /root/apue/fiecho "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.