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Top Forums Shell Programming and Scripting Perl: How to check if there is something being piped in Post 302721207 by zaxxon on Thursday 25th of October 2012 08:56:14 AM
Old 10-25-2012
Hey,

my problem is to catch the issue, that there is nothing being piped in. Example:
Code:
$ cat mach.pl
#!/usr/bin/perl

while( defined($line = <STDIN>) ) {
        chomp($line);
        print $line . "\n";
}

exit(0);

Yes, feeding it works:
Code:
$ echo yo | ./mach.pl
yo

This hangs and waits for input, like a grep in a shell waiting for input. Can only break it with Ctrl+c:
Code:
$ ./mach.pl

...

I am looking for a way to notice, that there is nothing to be read from STDIN so I can end the script with some error message.
 

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ELFEDIT(1)						       GNU Development Tools							ELFEDIT(1)

NAME
elfedit - Update the ELF header of ELF files. SYNOPSIS
elfedit [--input-mach=machine] [--input-type=type] [--input-osabi=osbi] --output-mach=machine --output-type=type --output-osabi=osbi [-v|--version] [-h|--help] elffile... DESCRIPTION
elfedit updates the ELF header of ELF files which have the matching ELF machine and file types. The options control how and which fields in the ELF header should be updated. elffile... are the ELF files to be updated. 32-bit and 64-bit ELF files are supported, as are archives containing ELF files. OPTIONS
The long and short forms of options, shown here as alternatives, are equivalent. At least one of the --output-mach, --output-type and --output-osabi options must be given. --input-mach=machine Set the matching input ELF machine type to machine. If --input-mach isn't specified, it will match any ELF machine types. The supported ELF machine types are, L1OM and x86-64. --output-mach=machine Change the ELF machine type in the ELF header to machine. The supported ELF machine types are the same as --input-mach. --input-type=type Set the matching input ELF file type to type. If --input-type isn't specified, it will match any ELF file types. The supported ELF file types are, rel, exec and dyn. --output-type=type Change the ELF file type in the ELF header to type. The supported ELF types are the same as --input-type. --input-osabi=osabi Set the matching input ELF file OSABI to osbi. If --input-osabi isn't specified, it will match any ELF OSABIs. The supported ELF OSABIs are, none, HPUX, NetBSD, Linux, Hurd, Solaris, AIX, Irix, FreeBSD, TRU64, Modesto, OpenBSD, OpenVMS, NSK, AROS and FenixOS. --output-osabi=osabi Change the ELF OSABI in the ELF header to type. The supported ELF OSABI are the same as --input-osabi. -v --version Display the version number of elfedit. -h --help Display the command line options understood by elfedit. @file Read command-line options from file. The options read are inserted in place of the original @file option. If file does not exist, or cannot be read, then the option will be treated literally, and not removed. Options in file are separated by whitespace. A whitespace character may be included in an option by surrounding the entire option in either single or double quotes. Any character (including a backslash) may be included by prefixing the character to be included with a backslash. The file may itself contain additional @file options; any such options will be processed recursively. SEE ALSO
readelf(1), and the Info entries for binutils. COPYRIGHT
Copyright (c) 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.3 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License". binutils-2.21.1 2011-09-24 ELFEDIT(1)
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