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Shell 判断文件是否存在的方法

2017-04-21 01:45 323 查看
方法一:

locate_library() { [ ! "$1*" = "`echo $1*`" ]; }


用法:

# Look for PAM (done weirdly due to distribution bugs (e.g. Debian) or the
# crypt library.
if find_func pam_start sysdeputil.o; then
locate_library /lib/libpam.so.0 && echo "/lib/libpam.so.0";
locate_library /usr/lib/libpam.so && echo "-lpam";
locate_library /usr/lib64/libpam.so && echo "-lpam";
# HP-UX ends shared libraries with .sl
locate_library /usr/lib/libpam.sl && echo "-lpam";
# AIX ends shared libraries with .a
locate_library /usr/lib/libpam.a && echo "-lpam";
else
locate_library /lib/libcrypt.so && echo "-lcrypt";
locate_library /usr/lib/libcrypt.so && echo "-lcrypt";
locate_library /usr/lib64/libcrypt.so && echo "-lcrypt";
fi


方法二:

#!/bin/sh

myPath="/var/log/httpd/"
myFile="/var/log/httpd/access.log"

#这里的-x 参数判断$myPath是否存在并且是否具有可执行权限
if [ ! -x "$myPath"]; then
  mkdir "$myPath"
fi

#这里的-d 参数判断$myPath是否存在
if [ ! -d "$myPath"]; then
  mkdir "$myPath"
fi

#这里的-f参数判断$myFile是否存在
if [ ! -f "$myFile" ]; then
  touch "$myFile"
fi

#其他参数还有-n,-n是判断一个变量是否是否有值
if [ ! -n "$myVar" ]; then
  echo "$myVar is empty"
  exit 0
fi

#两个变量判断是否相等
if [ "$var1" = "$var2" ]; then
  echo '$var1 eq $var2'
else
  echo '$var1 not eq $var2'
fi


各种判断标识及含义如下:

-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.
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