How portable is mktemp(1)?

Question

As the title suggests — can I be reasonably sure that mktemp will exist on any unix-y operating system I'm likely to encounter?

Bicapsular

See also unix.stackexchange.com/a/84980/37512. – Libratory

Answer 1

POSIX does not seem to specify mktemp(1).

It looks like most modern systems have it, but the available functionality and the semantics of the options vary between implementations (so particular invocations may not be portable):

• mktemp(1) from OpenBSD — mktemp(1) originated in OpenBSD 2.1
• mktemp(1) from FreeBSD
• mktemp(1) from Mac OS X — almost always the same as from FreeBSD
• mktemp(1) from Todd C. Miller of sudo fame
• mktemp(1) from Solaris
• mktemp(1) from GNU coreutils
• mktemp(1) from HP/UX — this one seems particularly divergent from most of the others listed here

So if you want a portable solution you may need to stick to functionality and options that mean the same thing on all of your platforms of interest.

Nonentity

It use to be reasonably portable and defined by POSIX but it seems that some weaknesses in it were addressed by forming a new function 'mkstemp()'. "4.3BSD, POSIX.1-2001. POSIX.1-2008 removes the specification of mktemp()." man7.org/linux/man-pages/man3/mktemp.3.html The newer replacment being man7.org/linux/man-pages/man3/mkstemp.3.html – Whitethorn

The mktemp @Whitethorn is addressing is the C library function, whereas the mktemp OP asked about is the command line program. – Betrothal

@Betrothal is one of things not often a very thin veneer around the other? – Whitethorn

@Whitethorn kind of. But it's not quite that thin. mktemp.c in gnu coreutils is 350 lines: lingrok.org/xref/coreutils/src/mktemp.c . And actually it doesn't look like it ever calls mktemp(3) instead it uses some gnulib function (not glibc) that does it's own logic and the only system call it makes is to open. – Betrothal

@Whitethorn No - no proper implementation of mktemp the command line tool will use mktemp the deprecated C function. – Langtry

HP/UX had mktemp(1) in 10.20 already (1996) and the revision control header in the man page had $Header: mktemp.1,v 72.3 93/01/14 11:27:33 ssa Exp $ suggesting it had been there for much longer. So HP/UX had a mktemp command long before OpenBSD (1997). – Itinerant

Todd Miller did write OpenBSD's mktemp in the first place and later made it a portable utility, the one used on Linux distributions until GNU wrote their own compatible one. – Itinerant

Actually, HP/UX 7.0 (1989) already had a mktemp utility and it looks like 6.x didn't. Ultrix 4.0 (1990) also had a mktemp with the same API. – Itinerant

Answer 2

A mktemp function (AKA mktemp(3)) first appeared in Unix V7 so it's likely to be everywhere. However, a mktemp command (aka mktemp(1)) first appeared, I believe, on OpenBSD 2.1, so if you have to deal with truly antediluvian Unix systems you might have to worry -- unless you can distribute the very portable mktemp.org version (to fix the potential lack of this utility on some customer's antediluvian system). How likely you are to encounter antediluvian system is nigh impossible for us to guess, of course -- e.g., in HP-UX, mktemp(1) has been around for at least 8 years (even most enterprises probably have updated their Unix OS's within that time frame), in Xenix I believe it appeared in 3.0 (in 1992), etc, etc.

Kindergarten

So the short summary is: yes, you can reasonably rely on mktemp being around – Novelette

Answer 3

FYI, mktemp appears to NOT be included with Solaris 9 (released 2002/2003) - just ran across this today:

$ uname -a
SunOS dcmnapp02 5.9 Generic_122300-47 sun4u sparc SUNW,Sun-Fire-V440
$ mktemp
bash: mktemp: command not found
$ man mktemp
bash-2.05$ man mktemp
Reformatting page.  Please Wait... done

Standard C Library Functions                           mktemp(3C)

NAME
     mktemp - make a unique file name

SYNOPSIS
     #include 

     char *mktemp(char *template);

Dissolution

Yes, Solaris 10 was the first Solaris release to include the mktemp(1) command in the OS. – Gulick

Answer 4

On Solaris 9 it's in package SMCmktemp, see http://sunfreeware.com/indexsparc9.html:

uname -s
SunOS
uname -r
5.9
/usr/sbin/pkgchk -l -p /usr/local/bin/mktemp
Pathname: /usr/local/bin/mktemp
Type: regular file
Expected mode: 0555
Expected owner: bin
Expected group: bin
Expected file size (bytes): 8884
Expected sum(1) of contents: 6493
Expected last modification: Nov 05 08:48:17 2002
Referenced by the following packages:
SMCmktemp
Current status: installed

Performance

Link is broken. – Aforementioned

Yes, the service has moved to unixpackages.com and has become a paid service. – Newby