Shell 判斷檔案是否存在的方法

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"  #這裡的-x 參數判斷$myPath是否存在並且是否具有可執行許可權  if [ ! -x "$myPath"]; then  　　mkdir "$myPath"  fi  #這裡的-d 參數判斷$myPath是否存在  if [ ! -d "$myPath"]; then  　　mkdir "$myPath"  fi  #這裡的-f參數判斷$myFile是否存在  if [ ! -f "$myFile" ]; then  　　touch "$myFile"  fi  #其他參數還有-n,-n是判斷一個變數是否是否有值  if [ ! -n "$myVar" ]; then  　　echo "$myVar is empty"  　　exit 0  fi  #兩個變數判斷是否相等  if [ "$var1" = "$var2" ]; then  　　echo '$var1 eq $var2'  else  　　echo '$var1 not eq $var2'  fi  

各種判斷標識及含義如下：

-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.