perl學習（2）檔案處理

1、讀取某檔案，如果該檔案不存在，則報錯，並提示出錯原因

open (DB, "/home/ellie/myfile") or die "Can't open file: $!\n";  

運行後提示：Can't open file: No such file or director 2、讀寫檔案的方法：

open(FH, "<filename");     # Opens "filename" for reading.讀
                           # The <; symbol is optional.



open(FH, ">filename");     # Opens "filename" for writing.寫
                           # Creates or truncates file.



open(FH, ">>filename");     # Opens "filename" for appending.追加
                            # Creates or appends to file.


open(FH, "+<filename");     # Opens "filename" for read, then write.寫讀後寫
open(FH, "+>filename");     # Opens "filename" for write, then read.先寫後讀


close(FH);                 

 3、開啟並列印該檔案

#!/usr/bin/perl

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

4、檔案屬性

#!/usr/bin/perl



my $file="d:/readtest.txt";


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


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


#若為目錄則列印
print "File is a directory.\n " if -d $file; # Is it a directory?

由於此檔案實際存在，並且是剛建不久，但只是普通的文字檔，因此最後的結果為File was last modified 0.0239930555555556 days ago.       若代碼：print "File is readable, writeable, and executable\n" if -r $file and -w _ and -x _;改為：print "File is readable, writeable, and executable\n" if -r $file and -w _ ;最後的結果則為：

File is readable, writeable, and executable

File was last modified 0.0251851851851852 days ago.

 

-w _為-w $file的簡寫。