open FILEHANDLE, EXPR, LIST
open FILEHANDLE, EXPR
Definition and Usage
Opens a file using the specified file handle. The file handle may be an expression, the resulting value is used as the handle. If no filename is specified a variable with the same name as the file handle used (this should be a scalar variable with a string value referring to the file name). The special file name '-' refers to STDIN and '>-' refers to STDOUT.
0 on failure
1 on success
Following is the syntax to open file.txt in read-only mode. Here less than < signe indicates that file has to be opend in read-only mode
Here DATA is the file handle which will be used to read the file. Here is the example which will open a file and will print its content over the screen.
Following is the syntax to open file.txt in writing mode. Here less than > signe indicates that file has to be opend in writing mode
This example actually truncates (empties) the file before opening it for writing, which may not be the desired effect. If you want to open a file for reading and writing, you can put a plus sign before the > or < characters.
For example, to open a file for updating without truncating it:
To truncate the file first:
open DATA, "+>file.txt" or die "Couldn't open file file.txt, $!";
You can open a file in append mode. In this mode writing point will be set to the end of the file
open(DATA,">>file.txt") || die "Couldn't open file file.txt, $!";
A double >> opens the file for appending, placing the file pointer at the end, so that you can immediately start appending information. However, you can.t read from it unless you also place a plus sign in front of it:
open(DATA,"+>>file.txt") || die "Couldn't open file file.txt, $!";
Following is the table which gives possible values of different modes
< or r Read Only Access
> or w Creates, Writes, and Truncates
>> or a Writes, Appends, and Creates
+< or r+ Reads and Writes
+> or w+ Reads, Writes, Creates, and Truncates
+>> or a+ Reads, Writes, Appends, and Creates