Linux man test

 

        先来看看Linux下对test的解释（使用man test或者info test）

 

 

TEST(1)                               FSF                              TEST(1)NAME       test - check file types and compare valuesSYNOPSIS       test EXPRESSION       [ EXPRESSION ]       test OPTIONDESCRIPTION       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 <[e-mail]>.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：

 

#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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