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Top Forums Shell Programming and Scripting Shells, forks, subprocesses... oh my Post 302993535 by Corona688 on Friday 10th of March 2017 05:54:35 PM
Old 03-10-2017
sed, bash, perl, awk, find, grep are all processes. A subshell is a process. A fork is a fork is a fork.

Whether any of these are faster or slower than other ways to solve your problem, really depends on your problem, and the algorithm you use to solve it. So "one solution to solve everything, forever" may be out the window.

There's some cardinal sins to avoid:
  • Don't reprocess the same file repeatedly. You can almost always do everything in one pass that you could do in two.
  • Don't launch whole processes to process tiny amounts of data. echo "a b c" | awk '{ print $1 }' is a tragic waste, this is when shell builtins would be thousands of times more efficient.
  • Running your innermost loop in the shell will be slow. A while read loop line by line over a file will be slower than awk '{ something }' filename. Shell is for the high level things, not the nitty gritty bulk work. This is when externals would be thousands of times more efficient.
  • If you're doing cat | awk | sed | cut | tr | kitchen | sink, put it all in one awk. awk is a programming language which is capable of replacing all of these with some near-trivial code, and one awk call will be faster than ten anything else.
  • Useless Use of Cat. Don't do that. Nothing needs a cat | in front of it to read a file.
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LOGPROF.CONF(5)                                                      AppArmor                                                      LOGPROF.CONF(5)

NAME
logprof.conf - configuration file for expert options that modify the behavior of the AppArmor aa-logprof(1) program. DESCRIPTION
The aa-logprof(1) program can be configured to have certain default behavior by the contents of logprof.conf. The [qualifiers] section lists specific programs that should have a subset of the full ix/px/ux list when asking what mode to execute it using. Since creating a separate profile for /bin/bash is dangerous, we can specify that for /bin/bash, only (I)nherit, (U)nconstrained, and (D)eny should be allowed options and only those will show up in the prompt when we're asking about adding that to a profile. Likewise, if someone currently exec's /bin/mount in ix or px mode, things won't work, so we can provide only (U)nconstrained and (D)eny as options. And certain apps like grep, awk, sed, cp, and mkdir should always inherit the parent profile rather than having their own profile or running unconfined, so for them we can specify that only (I)nherit and (D)eny are the allowed options. Any programs that are not listed in the qualifiers section get the full (I)nherit / (P)rofile / (U)nconstrained / (D)eny option set. If the user is doing something tricky and wants different behavior, they can tweak or remove the corresponding line in the conf file. The [defaulthat] section lists changehat-aware programs and what hat aa-logprof(1) will collapse the entries to for that program if the user specifies that the access should be allowed, but should not have it's own hat. The [globs] section allows modification of the logprof rule engine with respect to globbing suggestions that the user will be prompted with. The format of each line is-- "<perl glob> = <apparmor glob>". When aa-logprof(1) asks about a specific path, if the perl glob matches the path, it replaces the part of the path that matched with the corresponding apparmor glob and adds it to the list of globbing suggestions. Lines starting with # are comments and are ignored. EXAMPLE
[qualifiers] # things will very likely be painfully broken if bash has it's own profile /bin/bash = iu # mount doesn't work if it's confined /bin/mount = u # these helper utilities should inherit the parent profile and # shouldn't have their own profiles /bin/awk = i /bin/grep = i /bin/sed = i [defaulthat] /usr/sbin/sshd = EXEC /usr/sbin/httpd2 = DEFAULT_URI /usr/sbin/httpd2-prefork = DEFAULT_URI [globs] # /foo/bar/lib/libbaz.so -> /foo/bar/lib/lib* /lib/lib[^/]+so[^/]*$ = /lib/lib*so* # strip kernel version numbers from kernel module accesses ^/lib/modules/[^/]+/ = /lib/modules/*/ # strip pid numbers from /proc accesses ^/proc/d+/ = /proc/*/ BUGS
If you find any bugs, please report them at <http://https://bugs.launchpad.net/apparmor/+filebug>. SEE ALSO
apparmor(7), apparmor.d(5), aa-enforce(1), aa-complain(1), aa-disable(1), aa_change_hat(2), aa-logprof(1), aa-genprof(1), and <http://wiki.apparmor.net>. AppArmor 2.7.103 2012-06-28 LOGPROF.CONF(5)
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