To access and manipulate files in a Perl program, there is a three step process: 1. Open the file using the open() function, which establishes access to the file. 2. Read from or write to the file as needed. 3. Close the file using close() to release access when done. The document provides examples of opening files for reading, writing, and appending using open() and specifies modes like > and >>. It also gives a short script that demonstrates copying the first three lines of one file to another as an example of file handling in Perl.

1. 18IS33-UNIX and Shell Programming (Scheme and Solution) Page 10
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Subject Titles: UNIX and Shell Programming. Subject Code: 18IS33
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10.c) File andling
To access a file on your UNIX file system from within your Perl program, you must perform the
following steps:
1. First, your program must open the file. This tells the system that your Perl program wants to
access the file.
2. Then, the program can either read from or write to the file, depending on how you have
opened the file.
3. Finally, the program can close the file. This tells the system that your program no longer
needs access to the file.
To open a file we use the open() function. open(INFILE, /home/srm/input.dat”);
INFILE is the file handle. The second argument is the pathname. If only the filename is
supplied, the file is assumed to be in the current working directory.
open(OUTFILE,”>report.dat”); # Opens the file in write mode open(OUTFILE,”>>report.dat”);
# Opens the file in append mode
The following script demonstrates file handling in perl. This script copies the first three lines of
one file into another.
#!/usr/bin/perl
open(INFILE, “desig.dat”) || die(“Cannot open file”);
open(OUTFILE, “>desig_out.dat”);
while(<INFILE>) {
print OUTFILE if(1..3);
} close(INFILE); close(OUTFILE);
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