perl学习（2）文件处理

bsbforever

　　1、读取某文件，如果该文件不存在，则报错，并提示出错原因
  
   open (DB, "/home/ellie/myfile") or die "Can't open file: $!\n";  


运行后提示：Can't open file: No such file or director



2、读写文件的方法：


　　open(FH, &quot;<filename&quot;);     # Opens &quot;filename&quot; for reading.读
                           # The <; symbol is optional.
　　

open(FH, &quot;>filename&quot;);     # Opens &quot;filename&quot; for writing.写
                           # Creates or truncates file.
　　

open(FH, &quot;>>filename&quot;);     # Opens &quot;filename&quot; for appending.追加
                            # Creates or appends to file.
　　
open(FH, &quot;+<filename&quot;);     # Opens &quot;filename&quot; for read, then write.写读后写
open(FH, &quot;+>filename&quot;);     # Opens &quot;filename&quot; for write, then read.先写后读
　　
close(FH);                 




3、打开并打印该文件


#!/usr/bin/perl
open(FH, &quot;<d:/readtest.txt&quot;) or die &quot;Can't open file: $!\n&quot;;
while(<FH>){ print }

4、文件属性




　　#!/usr/bin/perl
　　

my $file=&quot;d:/readtest.txt&quot;;
　　

# Is it readble, writeable, and executable?
print &quot;File is readable, writeable, and executable\n&quot; if -r $file and -w _ and -x _;
　　

# When was it last modified?
print &quot;File was last modified &quot;,-M $file, &quot; days ago.\n&quot;;
　　

#若为目录则打印
print &quot;File is a directory.\n &quot; if -d $file; # Is it a directory?



由于此文件实际存在，并且是刚建不久，但只是普通的文本文件，因此最后的结果为

File was last modified 0.0239930555555556 days ago.      



若代码：print &quot;File is readable, writeable, and executable\n&quot; if -r $file and -w _ and -x _;



改为：print &quot;File is readable, writeable, and executable\n&quot; if -r $file and -w _ ;

最后的结果则为：　　File is readable, writeable, and executable
File was last modified 0.0251851851851852 days ago.
　　
　　-w _为-w $file的简写。