1 .\" Copyright (c) 1999 Andries Brouwer (aeb@cwi.nl)
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25 .TH TEMPNAM 3 2013-04-19 "" "Linux Programmer's Manual"
27 tempnam \- create a name for a temporary file
32 .BI "char *tempnam(const char *" dir ", const char *" pfx );
36 Feature Test Macro Requirements for glibc (see
37 .BR feature_test_macros (7)):
41 _BSD_SOURCE || _SVID_SOURCE
45 function returns a pointer to a string that is a valid filename,
46 and such that a file with this name did not exist when
49 The filename suffix of the pathname generated will start with
53 is a non-NULL string of at most five bytes.
54 The directory prefix part of the pathname generated is required to
55 be "appropriate" (often that at least implies writable).
57 Attempts to find an appropriate directory go through the following
61 In case the environment variable
64 contains the name of an appropriate directory, that is used.
69 argument is non-NULL and appropriate, it is used.
76 is used when appropriate.
79 Finally an implementation-defined directory may be used.
81 The string returned by
85 and hence should be freed by
90 function returns a pointer to a unique temporary filename.
91 It returns NULL if a unique name cannot be generated, with
93 set to indicate the cause of the error.
97 Allocation of storage failed.
99 SVr4, 4.3BSD, POSIX.1-2001.
106 generates names that are difficult to guess,
107 it is nevertheless possible that between the time that
109 returns a pathname, and the time that the program opens it,
110 another program might create that pathname using
112 or create it as a symbolic link.
113 This can lead to security holes.
114 To avoid such possibilities, use the
117 flag to open the pathname.
123 SUSv2 does not mention the use of
125 glibc will use it only
126 when the program is not set-user-ID.
127 On SVr4, the directory used under \fBd)\fP is
129 (and this is what glibc does).
131 Because it dynamically allocates memory used to return the pathname,
133 is reentrant, and thus thread safe, unlike
138 function generates a different string each time it is called,
144 If it is called more than
147 the behavior is implementation defined.
150 uses at most the first five bytes from
153 The glibc implementation of
155 will fail with the error
157 upon failure to find a unique name.
159 The precise meaning of "appropriate" is undefined;
160 it is unspecified how accessibility of a directory is determined.
162 Never use this function.