Linux man test


Linux man test
 
        先来看看Linux下对test的解释（使用man test或者info test）
 
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TEST(1)                               FSF                              TEST(1)  
  
NAME  
       test - check file types and compare values  
  
SYNOPSIS  
       test EXPRESSION  
       [ EXPRESSION ]  
       test OPTION  
  
DESCRIPTION  
       Exit with the status determined by EXPRESSION.  
  
       --help display this help and exit  
  
       --version  
              output version information and exit  
  
       EXPRESSION is true or false and sets exit status.  It is one of:  
  
       ( EXPRESSION )  
              EXPRESSION is true  
  
       ! EXPRESSION  
              EXPRESSION is false  
  
       EXPRESSION1 -a EXPRESSION2  
  
       EXPRESSION1 -o EXPRESSION2  
              either EXPRESSION1 or EXPRESSION2 is true  
  
       [-n] STRING  
              the length of STRING is nonzero  
  
       -z STRING  
              the length of STRING is zero  
  
       STRING1 = STRING2  
              the strings are equal  
  
       STRING1 != STRING2  
              the strings are not equal  
  
       INTEGER1 -eq INTEGER2  
              INTEGER1 is equal to INTEGER2  
  
       INTEGER1 -ge INTEGER2  
              INTEGER1 is greater than or equal to INTEGER2  
  
       INTEGER1 -gt INTEGER2  
              INTEGER1 is greater than INTEGER2  
  
       INTEGER1 -le INTEGER2  
              INTEGER1 is less than or equal to INTEGER2  
  
       INTEGER1 -lt INTEGER2  
              INTEGER1 is less than INTEGER2  
  
       INTEGER1 -ne INTEGER2  
              INTEGER1 is not equal to INTEGER2  
  
       FILE1 -ef FILE2  
              FILE1 and FILE2 have the same device and inode numbers  
  
       FILE1 -nt FILE2  
              FILE1 is newer (modification date) than FILE2  
  
       FILE1 -ot FILE2  
              FILE1 is older than FILE2  
  
       -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  
  
       -h FILE  
              FILE exists and is a symbolic link (same as -L)  
  
       -G FILE  
              FILE exists and is owned by the effective group ID  
  
       -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 is readable  
  
       -s FILE  
              FILE exists and has a size greater than zero  
  
       -S FILE  
              FILE exists and is a socket  
  
       -t [FD]  
              file descriptor FD (stdout by default) is opened on a terminal  
  
       -u FILE  
              FILE exists and its set-user-ID bit is set  
  
       -w FILE  
              FILE exists and is writable  
  
       -x FILE  
              FILE exists and is executable  
       Beware  that  parentheses need to be escaped (e.g., by backslashes) for  
       shells.  INTEGER may also be -l STRING, which evaluates to  the  length  
       of STRING.  
  
AUTHOR  
       Written by FIXME: ksb and mjb.  
  
REPORTING BUGS  
       Report bugs to <bug-coreutils@gnu.org>.  
  
COPYRIGHT  
       Copyright (C) 2002 Free Software Foundation, Inc.  
       This is free software; see the source for copying conditions.  There is  
       NO warranty; not even for MERCHANTABILITY or FITNESS FOR  A  PARTICULAR  
       PURPOSE.  
  
SEE ALSO  
       The  full documentation for test is maintained as a Texinfo manual.  If  
       the info and test programs are properly installed  at  your  site,  the  
       command  
  
              info test  
  
       should give you access to the complete manual.  
  
GNU coreutils 4.5.3              February 2003                         TEST(1)  
 
 
        再看两个简单的例子：
 
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#示例一  
#!/bin/bash    
#iftest2    
echo -n "Enter your name:"    
read NAME    
#did the user just hit return    
if [ "$NAME" == "" ];    
then    
        echo "You did not enter any infomation"    
else    
        echo "Your name is ${NAME}"    
  
#示例二  
#!/bin/bash    
#ifelif    
echo -n "Enter your name:"    
read NAME    
if [ -z $NAME ] || [ "$NAME" = "" ];    
then    
        echo "You did not enter a name."    
elif [ "$NAME" = "root" ];    
then    
        echo "Hello root"    
elif [ "$NAME" = "chinaitlab" ];    
then    
        echo "Hello chinaitlab"    
else    
        echo "You are not root or wgb,but hi,$NAME"    
fi    
 
        小技巧：
        1.Linux对Shell的要求很严格，不要把代码洁癖（比如定义变量的空格、if、while等等中为了美观留下的空格）带到Linux Shell编程中，稍不注意就会报错；
 
        2.多用man或者info，会收到意想不到的收获。
 

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