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TMPNAM(3) - man page online | library functions

Create a name for a temporary file.

Chapter
2015-03-02
TMPNAM(3)                           Linux Programmer's Manual                           TMPNAM(3)

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 s is NULL, this name is generated in an internal static buffer and may be overwritten by the next call to tmp‐ nam(). If s is not NULL, the name is copied to the character array (of length at least L_tmpnam) pointed to by s and the value s is returned in case of success. The pathname that is created, has a directory prefix P_tmpdir. (Both L_tmpnam and P_tmpdir are defined in <stdio.h>, just like the TMP_MAX mentioned 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). ┌───────────┬───────────────┬──────────────────────────┐ │Interface │ Attribute │ Value │ ├───────────┼───────────────┼──────────────────────────┤ │tmpnam() │ Thread safety │ MT-Unsafe race:tmpnam/!s │ ├───────────┼───────────────┼──────────────────────────┤ │tmpnam_r() │ Thread safety │ MT-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_MAX times. If it is called more than TMP_MAX times, 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 sym‐ bolic link. This can lead to security holes. To avoid such possibilities, use the open(2) O_EXCL flag 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_THREADS or _POSIX_THREAD_SAFE_FUNCTIONS is 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. To get a glibc pro‐ totype for this function from <stdio.h>, define _SVID_SOURCE or _BSD_SOURCE (before including any header file).
BUGS Never use this function. Use mkstemp(3) or tmpfile(3) instead.
SEE ALSO mkstemp(3), mktemp(3), tempnam(3), tmpfile(3)
COLOPHON This page is part of release 4.04 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at http://www.kernel.org/doc/man-pages/.
2015-03-02 TMPNAM(3)
This manual Reference Other manuals
tmpnam(3) referred by environ(7) | explain(1) | explain(3) | explain_tmpnam(3) | explain_tmpnam_or_die(3) | getpid(2) | mkdtemp(3) | mkstemp(3) | mktemp(3) | ns_mktemp(3aolserver) | tempnam(3) | tmpfile(3)
refer to attributes(7) | mkstemp(3) | mktemp(3) | open(2) | tempnam(3) | tmpfile(3)