关于read函数

xuexi11

文件内容：

程序
$line=<FILE>;;print$line,"\n" ;
seek(FILE,0,0);
read(FILE,$seq,5,0);  print $seq,"\n";

read(FILE,$seq,5,3);  print $seq,"\n";
read(FILE,$seq,5,-3);  print $seq,"\n";
结果：
0123456789abcdefgh
01234
01256789
01256abcde

我认为应该是
0123456789abcdefgh
01234                (前5个)
89abc                 (跳过3个，读5个)
abcdef                (倒退3个，读5个)

我用的winxp，怎么才能得到后面的结果？
多谢

Osment

read 的第四个参数在非Unix平台下好象是不起作用的。。

luo1110

我现在Linux和Winxp下运行的结果和贴主的结果完全一样!
0123456789abcdefgh
01234
01256789
01256abcde

学无止境啊！

luo1110

我知道了。
read
Syntax
Category  list operator (i/o)
Arguments  handle, variable, length, offset
Arguments  handle, variable, length
Return Value  1 (true) '' (false)

Definition
Reads length bytes from file handle into variable (starting at offset if specified). It returns the number of bytes actually read.

你们看以下程序的运行结果
open(FILE,"< test.txt" ||  die("error";
$line=<FILE>;;print$line,"\n" ;
seek(FILE,0,0);
#read(FILE,$seq,5);  print $seq,"\n";
#read(FILE,$seq,5);  print $seq,"\n";

read(FILE,$seq1,5,0);  print $seq1,"\n";

read(FILE,$seq2,5,3);  print $seq2,"\n";
read(FILE,$seq2,5,-3);  print $seq2,"\n";
read(FILE,$seq3,5,-3);  print $seq3,"\n";

close(FILE);
#0123456789abcdefgh

结果为
0123456789abcdefgh
01234
       56789
       56abcde
Offset outside string at 2.pl line 11,<FILE>; line 1.

看来第四个参数的offset意思很特别哦！