BSD progname (getprogname, setprogname) - Revision history

Huntertur: /* How NetBSD does it */ Remove incorrect statement about this not being mentioned in the man page

2023-06-26T04:00:56Z

How NetBSD does it: Remove incorrect statement about this not being mentioned in the man page

← Older revision		Revision as of 04:00, 26 June 2023
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	<code>getprogname</code> simply returns <code>__progname</code>.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/getprogname.c?rev=1.5&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>		<code>getprogname</code> simply returns <code>__progname</code>.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/getprogname.c?rev=1.5&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>

	<code>setprogname</code> has functionality for setting <code>__progname</code>, including using <code>strrchr</code> to get the location of the last occurrence of <code>/</code>. This is to normalize a program run from <code>./blah/bin/hello</code> to just <code>hello</code>, which is actually useful added value ~~that isn't mentioned in the man page~~. However, unless the source file is modified, this functionality is never used, since a constant defined in the file makes the function a no-op.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/setprogname.c?rev=1.3&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref> <code>__progname</code> gets set in <code>crt0</code> using the same rule that the <code>setprogname</code> would have followed, but with a manual search, and with an extra rule that sets <code>__progname</code> to an empty string (pointer to <code>\0</code>) instead of <code>NULL</code> if the program name really is <code>NULL</code>, making the point in the man page about <code>getprogname</code> possibly returning <code>NULL</code> moot.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/common/crt0-common.c?rev=1.27&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>		<code>setprogname</code> has functionality for setting <code>__progname</code>, including using <code>strrchr</code> to get the location of the last occurrence of <code>/</code>. This is to normalize a program run from <code>./blah/bin/hello</code> to just <code>hello</code>, which is actually useful added value. However, unless the source file is modified, this functionality is never used, since a constant defined in the file makes the function a no-op.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/setprogname.c?rev=1.3&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref> <code>__progname</code> gets set in <code>crt0</code> using the same rule that the <code>setprogname</code> would have followed, but with a manual search, and with an extra rule that sets <code>__progname</code> to an empty string (pointer to <code>\0</code>) instead of <code>NULL</code> if the program name really is <code>NULL</code>, making the point in the man page about <code>getprogname</code> possibly returning <code>NULL</code> moot.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/common/crt0-common.c?rev=1.27&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>

	== Quick test ==		== Quick test ==

Huntertur: Remove duplicate periods

2023-06-23T21:42:07Z

Remove duplicate periods

← Older revision		Revision as of 21:42, 23 June 2023
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	== Initial thoughts ==		== Initial thoughts ==

	The man page says the functions appeared in NetBSD 1.6 and seems to suggest that they store <code>argv[0]</code> verbatim, even if it is <code>NULL</code>, and that <code>setprogname</code> is useless because <code>crt0</code> calls it during C runtime initialization and because the program name is a write-once value.<ref>https://man.netbsd.org/NetBSD-9.3-STABLE/getprogname.3</ref> The functions then found their way into FreeBSD 4.4.<ref>https://man.freebsd.org/cgi/man.cgi?query=getprogname&apropos=0&sektion=3&manpath=FreeBSD+13.2-RELEASE+and+Ports&arch=default&format=html</ref>. Unlike NetBSD and FreeBSD, OpenBSD states that the functions originated as a wrapper for the 4.4BSD <code>__progname</code> interface, first appearing in OpenBSD 5.4.<ref>https://man.openbsd.org/OpenBSD-7.3/getprogname.3</ref>		The man page says the functions appeared in NetBSD 1.6 and seems to suggest that they store <code>argv[0]</code> verbatim, even if it is <code>NULL</code>, and that <code>setprogname</code> is useless because <code>crt0</code> calls it during C runtime initialization and because the program name is a write-once value.<ref>https://man.netbsd.org/NetBSD-9.3-STABLE/getprogname.3</ref> The functions then found their way into FreeBSD 4.4.<ref>https://man.freebsd.org/cgi/man.cgi?query=getprogname&apropos=0&sektion=3&manpath=FreeBSD+13.2-RELEASE+and+Ports&arch=default&format=html</ref> Unlike NetBSD and FreeBSD, OpenBSD states that the functions originated as a wrapper for the 4.4BSD <code>__progname</code> interface, first appearing in OpenBSD 5.4.<ref>https://man.openbsd.org/OpenBSD-7.3/getprogname.3</ref>

	== How NetBSD does it ==		== How NetBSD does it ==
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	<code>getprogname</code> simply returns <code>__progname</code>.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/getprogname.c?rev=1.5&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>		<code>getprogname</code> simply returns <code>__progname</code>.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/getprogname.c?rev=1.5&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>

	<code>setprogname</code> has functionality for setting <code>__progname</code>, including using <code>strrchr</code> to get the location of the last occurrence of <code>/</code>. This is to normalize a program run from <code>./blah/bin/hello</code> to just <code>hello</code>, which is actually useful added value that isn't mentioned in the man page. However, unless the source file is modified, this functionality is never used, since a constant defined in the file makes the function a no-op.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/setprogname.c?rev=1.3&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>. <code>__progname</code> gets set in <code>crt0</code> using the same rule that the <code>setprogname</code> would have followed, but with a manual search, and with an extra rule that sets <code>__progname</code> to an empty string (pointer to <code>\0</code>) instead of <code>NULL</code> if the program name really is <code>NULL</code>, making the point in the man page about <code>getprogname</code> possibly returning <code>NULL</code> moot.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/common/crt0-common.c?rev=1.27&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>		<code>setprogname</code> has functionality for setting <code>__progname</code>, including using <code>strrchr</code> to get the location of the last occurrence of <code>/</code>. This is to normalize a program run from <code>./blah/bin/hello</code> to just <code>hello</code>, which is actually useful added value that isn't mentioned in the man page. However, unless the source file is modified, this functionality is never used, since a constant defined in the file makes the function a no-op.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/setprogname.c?rev=1.3&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref> <code>__progname</code> gets set in <code>crt0</code> using the same rule that the <code>setprogname</code> would have followed, but with a manual search, and with an extra rule that sets <code>__progname</code> to an empty string (pointer to <code>\0</code>) instead of <code>NULL</code> if the program name really is <code>NULL</code>, making the point in the man page about <code>getprogname</code> possibly returning <code>NULL</code> moot.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/common/crt0-common.c?rev=1.27&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>

	== Quick test ==		== Quick test ==

Huntertur: Add example code

2023-06-23T04:39:35Z

Add example code

← Older revision		Revision as of 04:39, 23 June 2023
Line 10:		Line 10:

	<code>setprogname</code> has functionality for setting <code>__progname</code>, including using <code>strrchr</code> to get the location of the last occurrence of <code>/</code>. This is to normalize a program run from <code>./blah/bin/hello</code> to just <code>hello</code>, which is actually useful added value that isn't mentioned in the man page. However, unless the source file is modified, this functionality is never used, since a constant defined in the file makes the function a no-op.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/setprogname.c?rev=1.3&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>. <code>__progname</code> gets set in <code>crt0</code> using the same rule that the <code>setprogname</code> would have followed, but with a manual search, and with an extra rule that sets <code>__progname</code> to an empty string (pointer to <code>\0</code>) instead of <code>NULL</code> if the program name really is <code>NULL</code>, making the point in the man page about <code>getprogname</code> possibly returning <code>NULL</code> moot.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/common/crt0-common.c?rev=1.27&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>		<code>setprogname</code> has functionality for setting <code>__progname</code>, including using <code>strrchr</code> to get the location of the last occurrence of <code>/</code>. This is to normalize a program run from <code>./blah/bin/hello</code> to just <code>hello</code>, which is actually useful added value that isn't mentioned in the man page. However, unless the source file is modified, this functionality is never used, since a constant defined in the file makes the function a no-op.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/setprogname.c?rev=1.3&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>. <code>__progname</code> gets set in <code>crt0</code> using the same rule that the <code>setprogname</code> would have followed, but with a manual search, and with an extra rule that sets <code>__progname</code> to an empty string (pointer to <code>\0</code>) instead of <code>NULL</code> if the program name really is <code>NULL</code>, making the point in the man page about <code>getprogname</code> possibly returning <code>NULL</code> moot.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/common/crt0-common.c?rev=1.27&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>

			== Quick test ==

			Compile this and run it from different paths.

			<syntaxhighlight lang="c">
			#include <stdio.h>
			#include <stdlib.h>

			int main(int argc, char *argv[])
			{
			printf("progname is %s\n", getprogname());
			printf("argv[0] is %s\n", argv[0]);

			return EXIT_SUCCESS;
			}
			</syntaxhighlight>

	== References ==		== References ==

Huntertur: Create page

2023-06-23T04:31:33Z

Create page

New page

The '''BSD __progname interface''', composed of ('''getprogname''' and '''setprogname'''), stood out to me while reading the NetBSD source code. Why have functions for <code>argv[0]</code>? It turns out it does a little more.

== Initial thoughts ==

The man page says the functions appeared in NetBSD 1.6 and seems to suggest that they store <code>argv[0]</code> verbatim, even if it is <code>NULL</code>, and that <code>setprogname</code> is useless because <code>crt0</code> calls it during C runtime initialization and because the program name is a write-once value.<ref>https://man.netbsd.org/NetBSD-9.3-STABLE/getprogname.3</ref> The functions then found their way into FreeBSD 4.4.<ref>https://man.freebsd.org/cgi/man.cgi?query=getprogname&apropos=0&sektion=3&manpath=FreeBSD+13.2-RELEASE+and+Ports&arch=default&format=html</ref>. Unlike NetBSD and FreeBSD, OpenBSD states that the functions originated as a wrapper for the 4.4BSD <code>__progname</code> interface, first appearing in OpenBSD 5.4.<ref>https://man.openbsd.org/OpenBSD-7.3/getprogname.3</ref>

== How NetBSD does it ==

<code>getprogname</code> simply returns <code>__progname</code>.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/getprogname.c?rev=1.5&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>

<code>setprogname</code> has functionality for setting <code>__progname</code>, including using <code>strrchr</code> to get the location of the last occurrence of <code>/</code>. This is to normalize a program run from <code>./blah/bin/hello</code> to just <code>hello</code>, which is actually useful added value that isn't mentioned in the man page. However, unless the source file is modified, this functionality is never used, since a constant defined in the file makes the function a no-op.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/gen/setprogname.c?rev=1.3&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>. <code>__progname</code> gets set in <code>crt0</code> using the same rule that the <code>setprogname</code> would have followed, but with a manual search, and with an extra rule that sets <code>__progname</code> to an empty string (pointer to <code>\0</code>) instead of <code>NULL</code> if the program name really is <code>NULL</code>, making the point in the man page about <code>getprogname</code> possibly returning <code>NULL</code> moot.<ref>http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/csu/common/crt0-common.c?rev=1.27&content-type=text/x-cvsweb-markup&only_with_tag=MAIN</ref>

== References ==

<references />

[[Category:Unix]]