变量后面加:t是什么意思？

iveney

比如有个变量$test
$test:t
是什么意思？？

yongjian

never seen that notation before. Are you talking about bash shell?

seamonkey

在zsh中，:t相当于basename

a=/boot/vmlinuz-2.6.17-1-686
echo $a:t
vmlinuz-2.6.17-1-686

确切地说是叫Modifier

类似还有

a=/boot/vmlinuz-2.6.17-1-686
echo $a:h
boot

echo $a:r
/boot/vmlinuz-2.6

echo $a:e
17-1-686

echo $a:u
/BOOT/VMLINUZ-2.6.17-1-686

yongjian

good to know! Thanks!

晨想

man bash 里边的 Modifiers 栏目，都写出来了。可以看看。：）。

seamonkey

对，bash也一样，zsh多了几个，如l,u,Q等

yongjian

true but notation like $a:t does not actually work well under bash.. any options need to be turned on?

seamonkey

只能用在历史编辑中

1. $ /sbin/ifconfig
   
2. eth0 ...
   
3. ...
   
4. $ !!:t
   
5. ifconfig
   
6. bash: ifconfig: command not found

复制代码

以下来自Bash FAQ 3.3

D3) Why doesn't bash have csh variable modifiers?

Posix has specified a more powerful, albeit somewhat more cryptic,
mechanism cribbed from ksh, and bash implements it.

${parameter%word}
         Remove smallest suffix pattern.  The WORD is expanded to produce
         a pattern.  It then expands to the value of PARAMETER, with the
         smallest portion of the suffix matched by the pattern deleted.

        x=file.c
         echo ${x%.c}.o
         -->file.o

${parameter%%word}

        Remove largest suffix pattern.  The WORD is expanded to produce
         a pattern.  It then expands to the value of PARAMETER, with the
         largest portion of the suffix matched by the pattern deleted.

        x=posix/src/std
         echo ${x%%/*}
         -->posix

${parameter#word}
         Remove smallest prefix pattern.  The WORD is expanded to produce
         a pattern.  It then expands to the value of PARAMETER, with the
         smallest portion of the prefix matched by the pattern deleted.

        x=$HOME/src/cmd
         echo ${x#$HOME}
         -->/src/cmd

${parameter##word}
         Remove largest prefix pattern.  The WORD is expanded to produce
         a pattern.  It then expands to the value of PARAMETER, with the
         largest portion of the prefix matched by the pattern deleted.

        x=/one/two/three
         echo ${x##*/}
         -->three

Given
         a=/a/b/c/d
         b=b.xxx

        csh                     bash            result
         ---                     ----            ------
         $a:h                    ${a%/*}            /a/b/c
         $a:t                    ${a##*/}           d
         $b:r                    ${b%.*}            b
         $b:e                    ${b##*.}           xxx

yongjian

that makes sense now.