What do the letters in `fc` command stand for

commandposixzsh

I just came across the fc command which lets you edit the previous command and issue it afterwards.

It has its own FCEDIT environment variable for setting its editor, and a man page in POSIX Programmer's Manual (1p).

It creates a file in /tmp directory and executes the contents if the file is saved (:wq in vim).

Apart from that, it can number and list fc -l previously executed commands to choose from.

So it's really nice and handy command to know.

The question is what does its name really mean; how to associate the command with its function in mind?

"First-class"? or maybe even just as "Function" (what came to my mind after composing the previous sentence)?

The manual refers to it simply as "the fc utility".

Best Answer

Although the zshbuiltins(1) man page does not indicate it, the fc command is pretty much the same as its bash counterpart. Simply (F)ix (C)ommand.

Related Solutions

POSIX – What is the Point of the ‘cd’ External Command?

It serves primarily as making sure the POSIX tool-chest is available both inside and outside a shell (see the POSIX rationale for requiring those).

For cd, that is not tremendously useful but note that cd changes directories but has other side effects: it returns an exit status that helps determine whether you're able to chdir() to that directory or not, and outputs a useful error message explaining why you can't chdir() when you can't.

Example:

dirs_i_am_able_to_cd_into=$(find . -type d -exec cd {} \; -print)

Another potential side-effect is the automounting of a directory.

On a few systems, most of the external commands for the standard shell builtins are implemented as a symlink to the same script that does:

#! /bin/sh -
"${0##*/}" "$@"

That is start a shell and run the builtin in it.

Some other systems (like GNU), have utilities as true executable commands which can lead to confusions when the behavior differs from the shell builtin version.

Shell – Why is there no mktemp command in POSIX

That comes up regularly on the Austin Group mailing list, and I'm not under the impression the Open Group would be opposed to specifying it. It just needs someone to propose something. See for instance this message from Eric Blake (Red Hat, sits on the weekly POSIX meeting) from 2011 (here copied from gmane):

Date: Tue, 10 May 2011 07:13:32 -0600
From: Eric Blake <eblake-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
To: Nico Schottelius <nico-posix-xuaVFQXs+5hIG4jRRZ66WA@public.gmane.org>
Cc: austin-group-l-7882/jkIBncuagvECLh61g@public.gmane.org
Newsgroups: gmane.comp.standards.posix.austin.general
Subject: Re: No mktemp in posix?
Organization: Red Hat
Message-ID: <4DC939FC.2040407@redhat.com>
References: <20110510105051.GA1767@ethz.ch>
Xref: news.gmane.org gmane.comp.standards.posix.austin.general:4151

On 05/10/2011 04:50 AM, Nico Schottelius wrote:
> Good morning,
>
> digging through Issue 7, I haven't found any utility that gives
> the ability to create a secure, temporary file that is usually
> implemented in mktemp.

echo 'mkstemp(fileXXXXXX)' | m4

will output the name of a just-created temporary file.  However, I agree
that there does not seem to be any standardized utility that gives
mkdtemp functionality, which is often more useful than mkstemp (after
all, once you have a secure temporary directory, then you can create
secure fifos within that directory, rather than having to wish for a
counterpart 'mkftemp' function).

> Is there no mktemp utility by intent or can we add it in the
> next issue?

I know both BSD and GNU have a mktemp(1) that wraps mktemp(), mkstemp(),
and mkdtemp().  In my inbox, I have record of some off-list email in
February of this year regarding some work between those teams to try and
converge on some common functionality and to word that in a manner
appropriate for the standard, although I can't find any publicly
archived messages to that effect.  But yes, I think adding mktemp(1) to
the next revision of the standard would be worthwhile.  I'll try to
revive those efforts and actually post some proposed wording.

--
Eric Blake   eblake-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org    +1-801-349-2682
Libvirt virtualization library http://libvirt.org

In a more recent thread (worth reading), Geoff Clare (from the Open Group):

Date: Wed, 2 Nov 2016 15:13:46 +0000
From: Geoff Clare <gwc-7882/jkIBncuagvECLh61g@public.gmane.org>
To: austin-group-l-7882/jkIBncuagvECLh61g@public.gmane.org
Newsgroups: gmane.comp.standards.posix.austin.general
Subject: Re: [1003.1(2013)/Issue7+TC1 0001016]: race condition with set -C
Message-ID: <20161102151346.GB24416@lt.loopback>
Xref: news.gmane.org gmane.comp.standards.posix.austin.general:13408

Stephane Chazelas <stephane.chazelas-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote, on 02 Nov 2016:
>
> At the moment, there's no way (that I know) to create a temp file
> reliably with POSIX utilities

Given an m4 utility that conforms to the 2008 standard, there is:

tmpfile=$(echo 'mkstemp(/tmp/fooXXXXXX)' | m4)

However, I don't know how widespread support for the new mkstemp()
macro is.

--
Geoff Clare <g.clare-7882/jkIBncuagvECLh61g@public.gmane.org>
The Open Group, Apex Plaza, Forbury Road, Reading, RG1 1AX, England

(which is where I learned that trick which you're referring to in your question).

Best Answer

Related Solutions

POSIX – What is the Point of the ‘cd’ External Command?

Shell – Why is there no mktemp command in POSIX

Related Question