perl中$/的作用

$/在perl中是输入记录分隔符，影响perl对"行"的理解。默认是换行符"\n".也可以定义为其他的内容：

需要特别注意的是，$/的值是字符串，不是模式匹配。

1> 不修改$/的内容，默认为"\n"

eg: test.pl

open WRI, "<test.pl";
$content = <WRI>; #读取一行
@lines = <WRI>;  #将读取的所有行放入@lines数组中。
close WRI;
#foreach my $line (@lines){
#    print "$line";
#}

print "$content";

输出：

test]# perl test.pl
open WRI, "<test.pl";
test]#

2> 修改$/的值为某一字符串：

open WRI, "<test.pl";
print "$/";
local $/ = "7799";        #或者是local $/=7799
#$content = <WRI>;
@lines = <WRI>;
close WRI;
$l = 1 ;
foreach my $line (@lines){
    print "line $l: $line\n";
    $l++;
}

输出：

 test]# perl test.pl

line 1: open WRI, "<test.pl";
print "$/";
local $/ = "7799
line 2: ";
#$content = <WRI>;
@lines = <WRI>;
close WRI;
$l = 1 ;
foreach my $line (@lines){
    print "line $l: $line\n";
    $l++;
}

#print "$content";

 test]#

3> $\改成undef

open WRI, "<test.pl";
local $/ = undef;
#$content = <WRI>;
@lines = <WRI>;
close WRI;
$l = 1 ;
foreach my $line (@lines){
    print "line $l: $line\n";
    $l++;
}

#print "$content";

输出：

test]# perl test.pl
line 1: open WRI, "<test.pl";
local $/ = undef;
#$content = <WRI>;
@lines = <WRI>;
close WRI;
$l = 1 ;
foreach my $line (@lines){
    print "line $l: $line\n";
    $l++;
}

#print "$content";


eg2：

open WRI, "<test.pl";
local $/ = undef;
$content = <WRI>;
#@lines = <WRI>;
close WRI;
#$l = 1 ;
#foreach my $line (@lines){
#    print "line $l: $line\n";
#    $l++;
#}

print "$content";

输出：

test]# perl test.pl
open WRI, "<test.pl";
local $/ = undef;
$content = <WRI>;
#@lines = <WRI>;
close WRI;
#$l = 1 ;
#foreach my $line (@lines){
#    print "line $l: $line\n";
#    $l++;
#}

print "$content";

4>如果$/设为整数、存有整数的标量或可转换成整数的标量这些值的引用时，Perl会尝试读入记录而不是行，最大记录长度就是引用的那个整数。

eg:

open WRI, "<test.pl";
local $/ = \7;    #以7个记录为一行分开。
#$content = <WRI>;
@lines = <WRI>;
close WRI;
$l = 1 ;
foreach my $line (@lines){
    print "line $l: $line\n";
    $l++;
}

输出：

test]# perl test.pl
line 1: open WR
line 2: I, "<te
line 3: st.pl";
line 4:
local
line 5: $/ = \7
line 6: ;
#$con
line 7: tent =
line 8: <WRI>;

line 9: @lines
line 10: = <WRI>
line 11: ;
close
line 12:  WRI;
$
line 13: l = 1 ;
line 14:
foreac
line 15: h my $l
line 16: ine (@l
line 17: ines){

line 18:     pri
line 19: nt "lin
line 20: e $l: $
line 21: line\n"
line 22: ;
    $
line 23: l++;
}

line 24:
#print
line 25:  "$cont
line 26: ent";