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PERL shmread Function
Syntax
shmread ID, VAR, POS, SIZE
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Definition and Usage
Reads the shared memory segment ID into the scalar VAR at position POS for up to SIZE bytes.
Return Value
0 on failure
1 on success
Example
Try out following example:
#!/usr/bin/perl
# Assume this file name is writer.pl
use IPC::SysV;
#use these next two lines if the previous use fails.
eval 'sub IPC_CREAT {0001000}' unless defined &IPC_CREAT;
eval 'sub IPC_RMID {0}' unless defined &IPC_RMID;
$key = 12345
$size = 80;
$message = "Pennyfarthingale.";
# Create the shared memory segment
$key = shmget($key, $size, &IPC_CREAT | 0777 ) or
die "Can't shmget: $!";
# Place a string in itl
shmwrite( $id, $message, 0, 80 ) or die "Can't shmwrite: $!";
sleep 20;
# Delete it;
shmctl( $id, &OPC_RMID, 0 ) or die "Can't shmctl: $! ";
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Write a reader program which retrieves the memory segment corresponding to $key and reads its contents using shmread();.
#!/usr/bin/perl
# Assume this file name is reader.pl
$key = 12345;
$size = 80;
# Identify the shared memory segment
$id = shmget( $key, $size, 0777 ) or die "Can't shmget: $!";
# Read its contents itno a string
shmread($id, $var, 0, $size) or die "Can't shmread: $!";
print $var;
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Now First run writer.pl program in background and then reader.pl then it will produces following result.
$perl writer.pl&
$perl reader.pl
Pennyfrathingale
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