01-26-2015
BASH Execution Delay / Speedup
What the job does is take that line of the file that it's given as an argument and uses that to make seven or eight data accesses. Right now they're stubs, but in the future, they'll be accessing some hardware that may take awhile. Hence, spawning the job to run in background.
At first, I thought that running over 200 of these jobs as bogging down the machine. So I reduced the number, and reduced and reduced until I had a single job that made some accesses and exited. Still a huge delay at the end of the loop. But there's no testing there -- it's just supposed to return and run the loop again. The test for the line number in the file is in the inner loop. The outer loop continues reading a new copy of the external file *inside* the loop, not where the slowdown is occurring. Not knowing exactly what BASH is doing internally, I don't know what's going on at the head and footer of the loop. But it occasionally slows down a LOT.
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LEARN ABOUT NETBSD
checkbashisms
CHECKBASHISMS(1) General Commands Manual CHECKBASHISMS(1)
NAME
checkbashisms - check for bashisms in /bin/sh scripts
SYNOPSIS
checkbashisms script ...
checkbashisms --help|--version
DESCRIPTION
checkbashisms, based on one of the checks from the lintian system, performs basic checks on /bin/sh shell scripts for the possible presence
of bashisms. It takes the names of the shell scripts on the command line, and outputs warnings if possible bashisms are detected.
Note that the definition of a bashism in this context roughly equates to "a shell feature that is not required to be supported by POSIX";
this means that some issues flagged may be permitted under optional sections of POSIX, such as XSI or User Portability.
In cases where POSIX and Debian Policy disagree, checkbashisms by default allows extensions permitted by Policy but may also provide
options for stricter checking.
OPTIONS
--help, -h
Show a summary of options.
--newline, -n
Check for "echo -n" usage (non POSIX but required by Debian Policy 10.4.)
--posix, -p
Check for issues which are non POSIX but required to be supported by Debian Policy 10.4 (implies -n).
--force, -f
Force each script to be checked, even if it would normally not be (for instance, it has a bash or non POSIX shell shebang or appears
to be a shell wrapper).
--extra, -x
Highlight lines which, whilst they do not contain bashisms, may be useful in determining whether a particular issue is a false posi-
tive which may be ignored. For example, the use of "$BASH_ENV" may be preceded by checking whether "$BASH" is set.
--version, -v
Show version and copyright information.
EXIT VALUES
The exit value will be 0 if no possible bashisms or other problems were detected. Otherwise it will be the sum of the following error val-
ues:
1 A possible bashism was detected.
2 A file was skipped for some reason, for example, because it was unreadable or not found. The warning message will give details.
SEE ALSO
lintian(1).
AUTHOR
checkbashisms was originally written as a shell script by Yann Dirson <dirson@debian.org> and rewritten in Perl with many more features by
Julian Gilbey <jdg@debian.org>.
DEBIAN
Debian Utilities CHECKBASHISMS(1)