Relocate true(1) article
This commit is contained in:
parent
ff8f077829
commit
ebbe8d4033
@ -86,7 +86,6 @@ I'm vaccinated against COVID-19. Are you?
|
||||
<A HREF="knowledge/cat/" >cat(1)</A>,
|
||||
<A HREF="knowledge/c78" >c78</A>,
|
||||
<A HREF="knowledge/software">software</A>,
|
||||
<A HREF="knowledge/true" >true(1)</A>,
|
||||
<A HREF="knowledge/x200t" >X200T</A>;
|
||||
<B>shilling</B>:
|
||||
<A HREF="#stickers">#stickers</A>
|
||||
|
||||
@ -16,7 +16,6 @@
|
||||
<SCRIPT SRC="/js/sheets.js" TYPE="application/javascript"></SCRIPT>
|
||||
<SCRIPT TYPE="application/javascript">window.onload = window.initializesheets;</SCRIPT>
|
||||
<H1>software</H1>
|
||||
<H3>updated 2022-05-26</H3>
|
||||
<HR ALIGN="left" SIZE="1" WIDTH="25%" />
|
||||
<H2>Foreword</H2>
|
||||
<P>
|
||||
@ -35,6 +34,11 @@ Ultimately, the humans were the ones that produced the computers, and computers
|
||||
Try to be kind to everyone but don't take anything too seriously.
|
||||
</P>
|
||||
|
||||
<H2>UNIX</H2>
|
||||
<UL>
|
||||
<LI><A HREF="https://github.com/dspinellis/unix-history-repo">unix-history-repo</A> (GitHub)</LI>
|
||||
</UL>
|
||||
|
||||
<H2>ACPI client</H2>
|
||||
<P>
|
||||
An ACPI client is a program that displays computer ACPI information, typically power and thermal statuses.
|
||||
@ -299,6 +303,10 @@ Make sure that service is added to runlevel boot.
|
||||
Configuration is in <CODE>/etc/conf.d/dmcrypt</CODE> and further configuration should be done in <CODE><A HREF="#fstab">fstab</A></CODE>.
|
||||
<CODE>dm-crypt</CODE> will need the UUID of the <I>physical</I> block device while fstab (if being configured with UUIDs will need the UUID of the decrypted block device in the device mapper.
|
||||
</P>
|
||||
<H3>TestDisk</H3>
|
||||
<UL>
|
||||
<LI><A HREF="https://en.wikipedia.org/wiki/TestDisk">TestDisk</A> (Wikipedia)</LI>
|
||||
</UL>
|
||||
|
||||
<H2>PCI Utilities</H2>
|
||||
<UL>
|
||||
@ -342,12 +350,22 @@ Supplies <CODE>lspci(8)</CODE>, <CODE>setpci(8)</CODE>, and <CODE>update-pciids(
|
||||
<I>Do not</I> use SSL workarounds like (in the case of git) <CODE>GIT_SSL_NO_VERIFY</CODE>.
|
||||
These leave your system open to man-in-the-middle attacks.
|
||||
</P>
|
||||
<H3>rc.d</H3>
|
||||
<UL>
|
||||
<LI><A HREF="http://www.mewburn.net/luke/papers/rc.d.pdf">The Design and Implementation of the NetBSD rc.d system</A></LI>
|
||||
</UL>
|
||||
<H3>System logging</H3>
|
||||
<UL>
|
||||
<LI><A HREF="https://www.unitedbsd.com/d/548-system-instability-on-unstable-version-how-do-i-get-logs/7">System instability on unstable version - how do I get logs?</A></LI>
|
||||
</UL>
|
||||
<P>See <CODE>syslogd(8)</CODE> and <CODE>syslog.conf(5)</CODE>, which pertain to system logging.</P>
|
||||
<P>Setting <CODE>DDB_ONPANIC</CODE> (see <CODE>options(4)</CODE> and <CODE>sysctl(8)</CODE>) will save a crash dump at <CODE>/var/crash</CODE> on kernel panic.
|
||||
<H3>Upgrading</H3>
|
||||
<UL>
|
||||
<LI>The NetBSD Guide - <A HREF="https://www.netbsd.org/docs/guide/en/chap-upgrading.html">Chapter 4: Upgrading NetBSD</A></LI>
|
||||
<LI><A HREF="https://www.unitedbsd.com/d/110-upgrading-netbsd-using-sysinst">Upgrading NetBSD using sysinst</A></LI>
|
||||
</UL>
|
||||
|
||||
|
||||
<H2 ID="power">Power</H2>
|
||||
<P>Much of this can be configured in the ACPI settings in your <A HREF="#login_manager">login manager</A>, provided you have one running that can do this.</P>
|
||||
@ -401,6 +419,59 @@ Technically <CODE>cat(1)</CODE> and other UNIX utilities can be used in a hacky
|
||||
You'd be better off using <CODE>ed(1)</CODE>; the UX is very similar.
|
||||
</P>
|
||||
|
||||
<H2 ID="true">true(1)</H2>
|
||||
<UL>
|
||||
<LI><A HREF="http://trillian.mit.edu/~jc/;-)/ATT_Copyright_true.html">CHAMBERS John - The /bin/true Command and Copyright</A></LI>
|
||||
<LI><A HREF="https://twitter.com/rob_pike/status/966896123548872705">PIKE Rob - "/bin/true used to be an empty file."</A></LI>
|
||||
<LI><A HREF="https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html">RAITER Brian - A Whirlwind Tutorial on Creating Really Teensy ELF Executables for Linux</A></LI>
|
||||
<LI><A HREF="https://www.unix.com/man-page/posix/1p/true/">true(1p)</A> (The Open Group, 2003)</LI>
|
||||
<LI>Notable true implementations<UL>
|
||||
<LI><B>ongoing</B> started 1992 - <A HREF="https://www.gnu.org/">GNU</A>/<A HREF="https://www.gnu.org/software/coreutils/">coreutils</A> - <A HREF="https://git.savannah.gnu.org/cgit/coreutils.git/tree/src/true.c">src/true.c</A></LI>
|
||||
<LI><B>ongoing</B> forked from 4.4BSD-Lite2 - <A HREF="https://www.netbsd.org/">NetBSD</A>/<A HREF="https://github.com/NetBSD/src">src</A> - <A HREF="https://github.com/NetBSD/src/blob/trunk/usr.bin/true/true.sh">usr.bin/true/true.sh</A></LI>
|
||||
</UL></LI>
|
||||
</UL>
|
||||
<P>
|
||||
<CODE>true(1)</CODE> is a tool that <I>only</I> quits silently with an exit status of 0.
|
||||
Similarly, <CODE>false(1)</CODE> is a tool that <I>only</I> quits silently with an exit status of 1.
|
||||
Recognizing arguments, printing to standard output, reading from standard input, or otherwise exiting with any other status of 0, is a violation of the POSIX specification for <CODE>true(1)</CODE>.
|
||||
These utilities find use in shell scripting, which, though extremely relevant to these utilities, is beyond the scope of this article.
|
||||
</P>
|
||||
<P>
|
||||
Because <CODE>true(1)</CODE>'s required functionality is so simple a POSIX-compliant implementation is a one-liner in most languages, so long as you're willing to make an exception in your code styling.
|
||||
For example, in C:
|
||||
</P>
|
||||
<PRE><CODE CLASS="language-c" DATA-LANG="c">
|
||||
int main(void) { return 0; }
|
||||
</CODE></PRE>
|
||||
<P>
|
||||
Because executing an empty shellscript file will in most shells do nothing and return an exit status of 0, technically an empty shellscript file is a POSIX-compliant <CODE>true(1)</CODE> implementation in 0 bytes.
|
||||
This was the <CODE>true(1)</CODE> implementation on early versions of UNIX, including Research UNIX, System V, and Sun's Solaris, according to both Rob Pike and John Chambers.
|
||||
A more explicit implementation also exists in POSIX shell:
|
||||
</P>
|
||||
<PRE><CODE CLASS="language-shell" DATA-LANG="shell">
|
||||
#!/bin/sh
|
||||
exit 0
|
||||
</CODE></PRE>
|
||||
<P>
|
||||
This happens to be nearly identical in source to the implementation used by NetBSD.
|
||||
</P>
|
||||
<P>
|
||||
Python has the same 0 byte <CODE>true(1)</CODE> implementation feature as most shells.
|
||||
Here's <CODE><I>false</I>(1)</CODE> in Python rather than <CODE>true(1)</CODE> to demonstrate how exiting with an arbitrary exit status can be done:
|
||||
</P>
|
||||
<PRE><CODE CLASS="language-python" DATA-LANG="python">
|
||||
import sys
|
||||
sys.exit(1)
|
||||
</CODE></PRE>
|
||||
<P>
|
||||
In some shells, <CODE>true(1)</CODE> is a shell built-in command, so running <CODE>true</CODE> will run the shell author's implementation of <CODE>true(1)</CODE> rather than the system implementation.
|
||||
</P>
|
||||
<P>
|
||||
GNU <CODE>true(1)</CODE>, from the GNU coreutils, is well known for being a maximalist implementation - it's eighty lines long and directly includes four C header files.
|
||||
Their <CODE>true.c</CODE> is 2.3 kilobytes and parses the arguments <CODE>--help</CODE> and <CODE>--version</CODE> (only if either are the first argument to the program).
|
||||
The GNU coreutils implementation of <CODE>true(1)</CODE> is not POSIX compliant.
|
||||
</P>
|
||||
|
||||
<H2>util-linux</H2>
|
||||
<UL>
|
||||
<LI><A HREF="https://en.wikipedia.org/wiki/Util-linux">util-linux - Wikipedia</A></LI>
|
||||
@ -426,7 +497,7 @@ network={
|
||||
}
|
||||
</PRE>
|
||||
<P>
|
||||
See <CODE>wpa_supplicant.conf(5)<CODE>.
|
||||
See <CODE>wpa_supplicant.conf(5)</CODE>.
|
||||
</P>
|
||||
|
||||
<H2>X</H2>
|
||||
|
||||
@ -1,78 +0,0 @@
|
||||
<!DOCTYPE html>
|
||||
<HTML LANG="en">
|
||||
<HEAD>
|
||||
<LINK HREF="http://www.trinity.moe/knowledge/true" REL="canonical" />
|
||||
<LINK HREF="https://raw.githubusercontent.com/devenblake/homepage/main/favicon.ico" REL="shortcut icon" TYPE="image/x-icon" />
|
||||
<LINK HREF="/css/blank.css" ID="styling" REL="stylesheet" />
|
||||
<META CHARSET="UTF-8" />
|
||||
<META CONTENT="noindex" NAME="googlebot" /> <!-- FUCK GOOGLE -->
|
||||
<META CONTENT="interest-cohort=()" HTTP-EQUIV="Permissions-Policy" /> <!-- FUCK GOOGLE -->
|
||||
<META NAME="viewport" CONTENT="width=device-width, initial-scale=1" />
|
||||
<TITLE>true(1)</TITLE>
|
||||
</HEAD>
|
||||
<BODY>
|
||||
<P><A HREF="/">~ Return to the rest of the site</A></P>
|
||||
<SCRIPT SRC="/js/cookies.js" TYPE="application/javascript"></SCRIPT>
|
||||
<SCRIPT SRC="/js/sheets.js" TYPE="application/javascript"></SCRIPT>
|
||||
<SCRIPT TYPE="application/javascript">window.onload = window.initializesheets;</SCRIPT>
|
||||
<H1>POSIX true(1)</H1>
|
||||
<H3>updated 2021-08-18</H3>
|
||||
<HR ALIGN="left" SIZE="1" WIDTH="25%" />
|
||||
<P>
|
||||
<CODE>true(1)</CODE> is a tool that <I>only</I> quits silently with an exit status of 0.
|
||||
Similarly, <CODE>false(1)</CODE> is a tool that <I>only</I> quits silently with an exit status of 1.
|
||||
Recognizing arguments, printing to standard output, reading from standard input, or otherwise exiting with any other status of 0, is a violation of the POSIX specification for <CODE>true(1)</CODE>.
|
||||
These utilities find use in shell scripting, which, though extremely relevant to these utilities, is beyond the scope of this article.
|
||||
</P>
|
||||
<P>
|
||||
Because <CODE>true(1)</CODE>'s required functionality is so simple a POSIX-compliant implementation is a one-liner in most languages, so long as you're willing to make an exception in your code styling.
|
||||
For example, in C:
|
||||
</P>
|
||||
<PRE><CODE CLASS="language-c" DATA-LANG="c">
|
||||
int main(void) { return 0; }
|
||||
</CODE></PRE>
|
||||
<P>
|
||||
Because executing an empty shellscript file will in most shells do nothing and return an exit status of 0, technically an empty shellscript file is a POSIX-compliant <CODE>true(1)</CODE> implementation in 0 bytes.
|
||||
This was the <CODE>true(1)</CODE> implementation on early versions of UNIX, including Research UNIX, System V, and Sun's Solaris, according to both Rob Pike and John Chambers.
|
||||
A more explicit implementation also exists in POSIX shell:
|
||||
</P>
|
||||
<PRE><CODE CLASS="language-shell" DATA-LANG="shell">
|
||||
#!/bin/sh
|
||||
exit 0
|
||||
</CODE></PRE>
|
||||
<P>
|
||||
This happens to be nearly identical in source to the implementation used by NetBSD.
|
||||
</P>
|
||||
<P>
|
||||
Python has the same 0 byte <CODE>true(1)</CODE> implementation feature as most shells.
|
||||
Here's <CODE><I>false</I>(1)</CODE> in Python rather than <CODE>true(1)</CODE> to demonstrate how exiting with an arbitrary exit status can be done:
|
||||
</P>
|
||||
<PRE><CODE CLASS="language-python" DATA-LANG="python">
|
||||
import sys
|
||||
sys.exit(1)
|
||||
</CODE></PRE>
|
||||
<P>
|
||||
In some shells, <CODE>true(1)</CODE> is a shell built-in command, so running <CODE>true</CODE> will run the shell author's implementation of <CODE>true(1)</CODE> rather than the system implementation.
|
||||
</P>
|
||||
<P>
|
||||
GNU <CODE>true(1)</CODE>, from the GNU coreutils, deserves a special mention, as it's eighty lines long and directly includes four C header files.
|
||||
This is not a joke.
|
||||
Their <CODE>true.c</CODE> is 2.3 kilobytes, parses the arguments <CODE>--help</CODE> and <CODE>--version</CODE> (only if either are the first argument to the program), and I don't know how big the executable ends up being because the first thing I do when I take control of a GNU system is <CODE>dd if=/dev/null of="$(which true)";chmod +x "$(which true)"</CODE> (<B>use at your own risk</B>).
|
||||
The GNU coreutils implementation of <CODE>true(1)</CODE> is not POSIX compliant.
|
||||
</P>
|
||||
<H2>Cited media and further reading</H2><UL>
|
||||
<LI>Articles and posts<UL>
|
||||
<LI><A HREF="http://trillian.mit.edu/~jc/;-)/ATT_Copyright_true.html">CHAMBERS John - The /bin/true Command and Copyright</A></LI>
|
||||
<LI><A HREF="https://twitter.com/rob_pike/status/966896123548872705">PIKE Rob - "/bin/true used to be an empty file."</A></LI>
|
||||
<LI><A HREF="https://www.muppetlabs.com/~breadbox/software/tiny/teensy.html">RAITER Brian - A Whirlwind Tutorial on Creating Really Teensy ELF Executables for Linux</A></LI>
|
||||
</UL></LI>
|
||||
<LI>Manual pages<UL>
|
||||
<LI><A HREF="https://www.unix.com/man-page/posix/1p/true/">true(1p)</A> (The Open Group, 2003)</LI>
|
||||
</UL></LI>
|
||||
<LI>Notable true implementations<UL>
|
||||
<LI><B>ongoing</B> started 1992 - <A HREF="https://www.gnu.org/">GNU</A>/<A HREF="https://www.gnu.org/software/coreutils/">coreutils</A> - <A HREF="https://git.savannah.gnu.org/cgit/coreutils.git/tree/src/true.c">src/true.c</A></LI>
|
||||
<LI><B>ongoing</B> forked from 4.4BSD-Lite2 - <A HREF="https://www.netbsd.org/">NetBSD</A>/<A HREF="https://github.com/NetBSD/src">src</A> - <A HREF="https://github.com/NetBSD/src/blob/trunk/usr.bin/true/true.sh">usr.bin/true/true.sh</A></LI>
|
||||
</UL></LI>
|
||||
</UL>
|
||||
</BODY>
|
||||
</HTML>
|
||||
Loading…
Reference in New Issue
Block a user