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Top Forums Shell Programming and Scripting Problem with pipes on infinite streams Post 302407987 by tokland on Saturday 27th of March 2010 01:12:01 PM
Old 03-27-2010
Hi!

Quote:
Originally Posted by alister
If using GNU grep:
Code:
counter | grep -m1 '[27]'

If that's not available:
Code:
counter | sed -n '/[27]/{p;q;}'

Thanks, those are good solutions. However, the grep in my code was just an example, let's imagine you cannot change how the stream is generated:

stream_generator | head -n1

By the way, using process substitution "works":

head -n1 <(stream_generator)

but it keeps the generator running on the background until the next match.
 

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HEAD(1) 							   User Commands							   HEAD(1)

NAME
head - output the first part of files SYNOPSIS
head [OPTION]... [FILE]... DESCRIPTION
Print the first 10 lines of each FILE to standard output. With more than one FILE, precede each with a header giving the file name. With no FILE, or when FILE is -, read standard input. Mandatory arguments to long options are mandatory for short options too. -c, --bytes=[-]NUM print the first NUM bytes of each file; with the leading '-', print all but the last NUM bytes of each file -n, --lines=[-]NUM print the first NUM lines instead of the first 10; with the leading '-', print all but the last NUM lines of each file -q, --quiet, --silent never print headers giving file names -v, --verbose always print headers giving file names -z, --zero-terminated line delimiter is NUL, not newline --help display this help and exit --version output version information and exit NUM may have a multiplier suffix: b 512, kB 1000, K 1024, MB 1000*1000, M 1024*1024, GB 1000*1000*1000, G 1024*1024*1024, and so on for T, P, E, Z, Y. AUTHOR
Written by David MacKenzie and Jim Meyering. REPORTING BUGS
GNU coreutils online help: <http://www.gnu.org/software/coreutils/> Report head translation bugs to <http://translationproject.org/team/> COPYRIGHT
Copyright (C) 2017 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO
tail(1) Full documentation at: <http://www.gnu.org/software/coreutils/head> or available locally via: info '(coreutils) head invocation' GNU coreutils 8.28 January 2018 HEAD(1)
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