1TMPNAM(3) Linux Programmer's Manual TMPNAM(3)
2
6 tmpnam, tmpnam_r - create a name for a temporary file
7
9 #include <stdio.h>
10 char *tmpnam(char *s);
12 char *tmpnam_r(char *s);
13 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
15 tmpnam_r()
17 Since glibc 2.19:
18 _DEFAULT_SOURCE
19 Up to and including glibc 2.19:
20 _BSD_SOURCE || _SVID_SOURCE
21
23 Note: avoid using these functions; use mkstemp(3) or tmpfile(3) in‐
24 stead.
25 The tmpnam() function returns a pointer to a string that is a valid
27 filename, and such that a file with this name did not exist at some
28 point in time, so that naive programmers may think it a suitable name
29 for a temporary file. If the argument s is NULL, this name is gener‐
30 ated in an internal static buffer and may be overwritten by the next
31 call to tmpnam(). If s is not NULL, the name is copied to the charac‐
32 ter array (of length at least L_tmpnam) pointed to by s and the value s
33 is returned in case of success.
34 The created pathname has a directory prefix P_tmpdir. (Both L_tmpnam
36 and P_tmpdir are defined in <stdio.h>, just like the TMP_MAX mentioned
37 below.)
38 The tmpnam_r() function performs the same task as tmpnam(), but returns
40 NULL (to indicate an error) if s is NULL.
41
43 These functions return a pointer to a unique temporary filename, or
44 NULL if a unique name cannot be generated.
45
47 No errors are defined.
48
50 For an explanation of the terms used in this section, see at‐
51 tributes(7).
52 ┌───────────────────────────┬───────────────┬──────────────────────────┐
54 │Interface │ Attribute │ Value │
55 ├───────────────────────────┼───────────────┼──────────────────────────┤
56 │tmpnam() │ Thread safety │ MT-Unsafe race:tmpnam/!s │
57 ├───────────────────────────┼───────────────┼──────────────────────────┤
58 │tmpnam_r() │ Thread safety │ MT-Safe │
59 └───────────────────────────┴───────────────┴──────────────────────────┘
60
62 tmpnam(): SVr4, 4.3BSD, C89, C99, POSIX.1-2001. POSIX.1-2008 marks
63 tmpnam() as obsolete.
64 tmpnam_r() is a nonstandard extension that is also available on a few
66 other systems.
67
69 The tmpnam() function generates a different string each time it is
70 called, up to TMP_MAX times. If it is called more than TMP_MAX times,
71 the behavior is implementation defined.
72 Although these functions generate names that are difficult to guess, it
74 is nevertheless possible that between the time that the pathname is re‐
75 turned and the time that the program opens it, another program might
76 create that pathname using open(2), or create it as a symbolic link.
77 This can lead to security holes. To avoid such possibilities, use the
78 open(2) O_EXCL flag to open the pathname. Or better yet, use mk‐
79 stemp(3) or tmpfile(3).
80 Portable applications that use threads cannot call tmpnam() with a NULL
82 argument if either _POSIX_THREADS or _POSIX_THREAD_SAFE_FUNCTIONS is
83 defined.
84
86 Never use these functions. Use mkstemp(3) or tmpfile(3) instead.
87
89 mkstemp(3), mktemp(3), tempnam(3), tmpfile(3)
90
92 This page is part of release 5.13 of the Linux man-pages project. A
93 description of the project, information about reporting bugs, and the
94 latest version of this page, can be found at
95 https://www.kernel.org/doc/man-pages/.
96 2021-03-22 TMPNAM(3)