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);
printf部分域说明符
与类型
含义
d
输出整形
s
输出字符串
f
输出浮点数
c
字符
%.2f 保留2位小数，四舍五入
%10 s靠右对齐，10个字符字
结果：
D:\>perl printf.pl
10.79
A
this is a test,ten characters
Love perl
Love perl
102
12 # %o 将数字转换为八进制
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