PERL命令行

PERL命令行

perl命令行操作需要加上-e否则会寻找perl脚本文件，命令用单引号包围，双引号会被OS认为是变量

PERL命令行参数

1. -n参数

   -n参数相当于创建while循环

   while(<>) {
   	commands;
   }
   

2. -p参数

   -p参数创建while循环，下一步打印

   while(<>) {
   	command;
   } continue {
   	print or die
   }
   

3. -i参数

   直接对操作对象进行修改

perl特殊变量

Special variable	Meaning
$_	默认的输入和模式搜索空间
$.	读取的最后一个文件柄的当前输入行号
$/	输入记录的分隔符，默认为换行。
$	输出记录的分隔符，默认为换行。
$,	打印输出字段分隔符
$‘’	连接字符串中插值的数组元素的分隔符
$0	正在执行的Perl脚本的文件名称

换行

-n和-p选项虽然仅有很小的差别，但是产生的结果会有很大的不同

I Do Not Love You Except Because I Love You :
I do not love you except because I love you;
I go from loving to not loving you,
From waiting to not waiting for you
My heart moves from cold to fire.
I love you only because it's you the one I love;
I hate you deeply, and hating you
Bend to you, and the measure of my changing love for you
Is that I do not see you but love you blindly.
Maybe January light will consume
My heart with its cruel
Ray, stealing my key to true calm.
In this part of the story I am the one who
Dies, the only one, and I will die of love because I love you,
Because I love you, Love, in fire and blood.

双倍行距

设定输出分隔符

perl -pe '$/ = "
"' poem

当前读入行追加换行

perl -pe '$_ .= "
"' poem

or 

perl -ne 'print $_ .= "
"' poem

空行外两倍行距

匹配文本开头存在的行

perl -pe '$_ .= "
" if /./'

排除空行

perl -pe '$_ .= "
" unless /^$/' poem

多倍行距

perl -pe '$_ .= "
"x4 if /./' poem

移除空行

perl -ne 'print  if /./' poem
or
perl -ne 'print  unless /^$/' poem

文本单词间两倍间距

perl -pe 's/ /  /g' poem

移除单词间的空格

perl -pe 's/ +//g' poem

编号

所有行进行编号

perl -pe '$_ = "$. $_"' poem
or
perl -ne 'print $. $_' poem

非空行编号空行不保留

perl -ne 'print "$. $_" if /./' poem
or
perl -ne 'print "$. $_" if /S/' poem
or
perl -ne 'print "$. $_" unless /^$/' poem

上述命令执行的结果是文本原始的行数编号，所以不连续

perl -ne 'print ++$x." $_" if /./' poem
or
perl -ne 'print ++$x." $_" if /S/' poem
or
perl -ne 'print ++$x." $_" unless /^$/' poem

非空行编号空行保留

perl -pe '$_ = ++$x." $_" if /./'
or
perl -pe '$_ = ++$x." $_" if /S/'
or
perl -pe '$_ = ++$x." $_" unless /^$/'