'\" t .\" Copyright (c) 1999 Andries Brouwer (aeb@cwi.nl) .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" .\" 2003-11-15, aeb, added tmpnam_r .\" .TH tmpnam 3 2024-05-02 "Linux man-pages 6.8" .SH NAME tmpnam, tmpnam_r \- create a name for a temporary file .SH LIBRARY Standard C library .RI ( libc ", " \-lc ) .SH SYNOPSIS .nf .B #include .P .BI "[[deprecated]] char *tmpnam(char *" s ); .BI "[[deprecated]] char *tmpnam_r(char *" s ); .fi .P .RS -4 Feature Test Macro Requirements for glibc (see .BR feature_test_macros (7)): .RE .P .BR tmpnam_r () .nf Since glibc 2.19: _DEFAULT_SOURCE Up to and including glibc 2.19: _BSD_SOURCE || _SVID_SOURCE .fi .SH DESCRIPTION .B Note: avoid using these functions; use .BR mkstemp (3) or .BR tmpfile (3) instead. .P The .BR 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 .I s is NULL, this name is generated in an internal static buffer and may be overwritten by the next call to .BR tmpnam (). If .I s is not NULL, the name is copied to the character array (of length at least .IR L_tmpnam ) pointed to by .I s and the value .I s is returned in case of success. .P The created pathname has a directory prefix .IR P_tmpdir . (Both .I L_tmpnam and .I P_tmpdir are defined in .IR , just like the .B TMP_MAX mentioned below.) .P The .BR tmpnam_r () function performs the same task as .BR tmpnam (), but returns NULL (to indicate an error) if .I s is NULL. .SH RETURN VALUE These functions return a pointer to a unique temporary filename, or NULL if a unique name cannot be generated. .SH ERRORS No errors are defined. .SH ATTRIBUTES For an explanation of the terms used in this section, see .BR attributes (7). .TS allbox; lbx lb lb l l l. Interface Attribute Value T{ .na .nh .BR tmpnam () T} Thread safety MT-Unsafe race:tmpnam/!s T{ .na .nh .BR tmpnam_r () T} Thread safety MT-Safe .TE .SH STANDARDS .TP .BR tmpnam () C11, POSIX.1-2008. .TP .BR tmpnam_r () None. .SH HISTORY .TP .BR tmpnam () SVr4, 4.3BSD, C89, POSIX.1-2001. Obsolete in POSIX.1-2008. .TP .BR tmpnam_r () Solaris. .SH NOTES The .BR tmpnam () function generates a different string each time it is called, up to .B TMP_MAX times. If it is called more than .B TMP_MAX times, the behavior is implementation defined. .P Although these functions generate names that are difficult to guess, it is nevertheless possible that between the time that the pathname is returned and the time that the program opens it, another program might create that pathname using .BR open (2), or create it as a symbolic link. This can lead to security holes. To avoid such possibilities, use the .BR open (2) .B O_EXCL flag to open the pathname. Or better yet, use .BR mkstemp (3) or .BR tmpfile (3). .P Portable applications that use threads cannot call .BR tmpnam () with a NULL argument if either .B _POSIX_THREADS or .B _POSIX_THREAD_SAFE_FUNCTIONS is defined. .SH BUGS Never use these functions. Use .BR mkstemp (3) or .BR tmpfile (3) instead. .SH SEE ALSO .BR mkstemp (3), .BR mktemp (3), .BR tempnam (3), .BR tmpfile (3)