"Breaking "while read" also breaks the parent process"

Post #302437748 by pludi on Friday 16th of July 2010 04:37:25 AM

The reason your program is breaking is that the break will exit the loop, ending the read, which sends a SIGPIPE to myprogram, which usually is an exit condition.

Do you have influence on the code of the program being started? If so, have it create a file once it's done, for which you can wait.

If not you'll have to put the reading loop into the background, and have it signal the main program once it's done. Something like


trap waiting=0 USR1

  ./myprogram | while read -r
    [[ "$REPLY" == "up and running" ]] && kill -USR1 $ppid
) &

printf "Waiting for startup"
while [ $waiting -eq 1 ]
  printf '.'
  sleep 1

: # Stuff to be done here

wait #Wait for "myprogram" to exit

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Strings with embedded line breaks are hard to read. Use concatenation or HEREDOCs instead. my $foo = "Line one is quite long Line two"; # Bad my $foo = "Line one is quite long Line two"; # Better, but still hard to read my $foo = "Line one is quite long " . "Line two"; # Better still my $foo = <<'EOF'; # Use heredoc for longer passages Line one is quite long Line two Line three breaks the camel's back EOF CONFIGURATION
This Policy is not configurable except for the standard options. AUTHOR
Chris Dolan <cdolan@cpan.org> CREDITS
Initial development of this policy was supported by a grant from the Perl Foundation. COPYRIGHT
Copyright (c) 2007-2011 Chris Dolan. Many rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself. The full text of this license can be found in the LICENSE file included with this module. perl v5.16.3 2014-06Perl::Critic::Policy::ValuesAndExpressions::ProhibitImplicitNewlines(3)

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