Linux man test

ゞ浴缸里的玫瑰 2022-03-17 09:18 321阅读 0赞

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 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：

#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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