perl基础知识02【代码执行格式】

[oracle@localhost ~]$ perl --help

Usage: perl [switches] [--] [programfile] [arguments]

-0[octal] specify record separator (\0, if no argument)

-a autosplit mode with -n or -p (splits $_ into @F)

-C[number/list] enables the listed Unicode features

-c check syntax only (runs BEGIN and CHECK blocks)

-d[:debugger] run program under debugger

-D[number/list] set debugging flags (argument is a bit mask or alphabets)

-e program one line of program (several -e's allowed, omit programfile)

#这个参数也常用，当在后面执行命令行时；如

[oracle@localhost ~]$ perl -e' print "ok\n"'

ok

-f don't do $sitelib/sitecustomize.pl at startup

-F/pattern/ split() pattern for -a switch (//'s are optional)

-i[extension] edit <> files in place (makes backup if extension supplied)

#直接在原文件上做修改！做时记得做个备份

-Idirectory specify @INC/#include directory (several -I's allowed)

-l[octal] enable line ending processing, specifies line terminator

-[mM][-]module execute "use/no module..." before executing program

-n assume "while (<>) { ... }" loop around program

#当作是循环，此选项经常使用，假定一个文本有10行内容，那么如果要处理这10行，你就要加上此参数；

-p assume loop like -n but print line also, like sed

#暂时未看出是什么用处的

-P run program through C preprocessor before compilation

#在编译之前通过C预处理器运行

-s enable rudimentary parsing for switches after programfile

#待确定

-S look for programfile using PATH environment variable

#它会去$PATH目录中去寻找你要执行的程序，而不会在默认的当前目录

-t enable tainting warnings

#开启损坏警告

-T enable tainting checks

#开启损坏核对

-u dump core after parsing program

[oracle@localhost ~]$ cat perl01

#!/usr/bin/perl

print "what\n";

[oracle@localhost ~]$ perl -u perl01

Aborted

-U allow unsafe operations

-v print version, subversion (includes VERY IMPORTANT perl info)

#直接输入perl -v 输出版本信息

-V[:variable] print configuration summary (or a single Config.pm variable)

#：直接输入perl -V 输出配置汇总

-w enable many useful warnings (RECOMMENDED)

[oracle@localhost ~]$ cat perl01

#!/usr/bin/perl

print what;

[oracle@localhost ~]$ perl perl01

[oracle@localhost ~]$ perl -w perl01 #因为没有在print内容上加引号的告警,虽然直接执行没有报错！

Unquoted string "what" may clash with future reserved word at perl01 line 2.

Name "main::what" used only once: possible typo at perl01 line 2.

print() on unopened filehandle what at perl01 line 2.

-W enable all warnings #同上 (-w)

-x[directory] strip off text before #!perl line and perhaps cd to directory

#格式类似于：perl -xzbkdir perl01 #其中zbkdir为一目录名，具体用处还不详；

-X disable all warnings

[oracle@localhost ~]$ perl -X perl01

[oracle@localhost ~]$

[oracle@localhost ~]$ cat perl01

use warnings;

#!/usr/bin/perl

print what;

[oracle@localhost ~]$ perl perl01

Unquoted string "what" may clash with future reserved word at perl01 line 3.

Name "main::what" used only once: possible typo at perl01 line 3.

print() on unopened filehandle what at perl01 line 3.

[oracle@localhost ~]$ perl -X perl01 #忽略里边use warnings的告警提示;

兴例：

（1）-ne

[oracle@localhost ~]$ cat >01.txt

first

second

third

[oracle@localhost ~]$

[oracle@localhost ~]$ perl -e '

> print;

> ' 01.txt

[oracle@localhost ~]$

[oracle@localhost ~]$ perl -ne'

> print;

> ' 01.txt

first

second

third

[oracle@localhost ~]$

#可以看到只有加入了-n选项后才能将文中的内容循环的输出；

（2）-i

#在原文件基础上直接修改

[oracle@localhost ~]$ perl -i -ne'

> s/first/last/ig;

> print;

> ' 01.txt

[oracle@localhost ~]$ cat 01.txt

last

second

third

#以上操作要切记备份，以免悲剧发生！