perl的一些函数（一）

　　1. index 函数

　　　　index 主要用于字符串查找，返回从左->右查到子字符串的起始位置（起始位置0），可以带括号，也可以不带。当找不到会返回-1

使用方法：

index STR,SUBSTR,POSITION
index STR,SUBSTR

实例：

#!/usr/bin/perl
use strict;
my $str1="Love me, love my dog\n";
print "return the first child string location\n";
print index $str1,"ove";
print "\nreturn the first child string from start postition\n";
print index($str1,"ove",2);
print "\nif can't find return -1\n";
print index($str1,"LOVE");
print "\n";

结果：

D:\>perl index.pl
return the first child string location 查找ove， ove 总共有出现第一次出现1，第二次10
1
return the first child string from start postition
10 <-----------从第3个位置查找（L-0,o-1,v-2）
if can't find return -1
-1

2.rindex从后向前查找，使用方法和index一样

rindex STR,SUBSTR,POSITION
rindex STR,SUBSTR

#!/usr/bin/perl
use strict;
my $str1="Love me, love my dog\n";
print "return the first child string location\n";
print rindex $str1,"ove";
print "\nreturn the first child string from start postition\n";
print rindex($str1,"ove",4);
print "\nif can't find return -1\n";
print rindex($str1,"LOVE");
print "\n";

View Code

运行结果：

D:\>perl rindex.pl
return the first child string location
10
return the first child string from start postition
1
if can't find return -1
-1

2.printf 函数

printf FILEHANDLE FORMAT, LIST
printf FILEHANDLE
printf FORMAT, LIST

printf 是从C语言移植过来的，参数和使用方法与C语言一样；

%表示域说明的开始，域标识符有以下

#!/usr/bin/perl
use strict;
my $float_number="10.789";
printf("%.2f\n",$float_number);
printf("%c\n",65);
printf("%10s\n","this is a test,ten characters");
printf("%-30s\n","Love perl");
printf("%30s\n","Love perl");
printf("%d\n",102.88);
printf("%o\n",10);