Manpage of TMPNAM

TMPNAM

Section: Linux Programmer's Manual (3)
Updated: 2016-03-15
Index
 

NAME

tmpnam, tmpnam_r - create a name for a temporary file  

SYNOPSIS

#include <stdio.h>char *tmpnam(char *s);
 

DESCRIPTION

Note:Avoid use of tmpnam(); use mkstemp(3) or tmpfile(3) instead.

The tmpnam() function returns a pointer to a string that is a valid filename, and such that a file with this name did not exist at some point in time, so that naive programmers may think it a suitable name for a temporary file. If the argument sis NULL, this name is generated in an internal static buffer and may be overwritten by the next call to tmpnam(). If sis not NULL, the name is copied to the character array (of length at least L_tmpnam) pointed to by sand the value sis returned in case of success.

The pathname that is created, has a directory prefix P_tmpdir. (Both L_tmpnamand P_tmpdirare defined in <stdio.h>, just like the TMP_MAXmentioned below.)  

RETURN VALUE

The tmpnam() function returns a pointer to a unique temporary filename, or NULL if a unique name cannot be generated.  

ERRORS

No errors are defined.  

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
InterfaceAttributeValue
tmpnam() Thread safetyMT-Unsafe race:tmpnam/!s
tmpnam_r() Thread safetyMT-Safe
 

CONFORMING TO

SVr4, 4.3BSD, C89, C99, POSIX.1-2001. POSIX.1-2008 marks tmpnam() as obsolete.  

NOTES

The tmpnam() function generates a different string each time it is called, up to TMP_MAXtimes. If it is called more than TMP_MAXtimes, the behavior is implementation defined.

Although tmpnam() generates names that are difficult to guess, it is nevertheless possible that between the time that tmpnam() returns a pathname, and the time that the program opens it, another program might create that pathname using open(2), or create it as a symbolic link. This can lead to security holes. To avoid such possibilities, use the open(2) O_EXCLflag to open the pathname. Or better yet, use mkstemp(3) or tmpfile(3).

Portable applications that use threads cannot call tmpnam() with a NULL argument if either _POSIX_THREADSor _POSIX_THREAD_SAFE_FUNCTIONSis defined.

A POSIX draft proposed to use a function tmpnam_r() defined by

char *
tmpnam_r(char *s)
{
    return s ? tmpnam(s) : NULL;
}

apparently as a warning not to use NULL. A few systems implement it and an implementation is provided in glibc.  

BUGS

Never use this function. Use mkstemp(3) or tmpfile(3) instead.  

SEE ALSO

mkstemp(3), mktemp(3), tempnam(3), tmpfile(3)


 

Index

NAME
SYNOPSIS
DESCRIPTION
RETURN VALUE
ERRORS
ATTRIBUTES
CONFORMING TO
NOTES
BUGS
SEE ALSO

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Time: 22:27:54 GMT, June 20, 2016