1MKDTEMP(3P) POSIX Programmer's Manual MKDTEMP(3P)
2
6 This manual page is part of the POSIX Programmer's Manual. The Linux
7 implementation of this interface may differ (consult the corresponding
8 Linux manual page for details of Linux behavior), or the interface may
9 not be implemented on Linux.
10
12 mkdtemp, mkstemp — create a unique directory or file
13
15 #include <stdlib.h>
16 char *mkdtemp(char *template);
18 int mkstemp(char *template);
19
21 The mkdtemp() function shall create a directory with a unique name
22 derived from template. The application shall ensure that the string
23 provided in template is a pathname ending with at least six trailing
24 'X' characters. The mkdtemp() function shall modify the contents of
25 template by replacing six or more 'X' characters at the end of the
26 pathname with the same number of characters from the portable filename
27 character set. The characters shall be chosen such that the resulting
28 pathname does not duplicate the name of an existing file at the time of
29 the call to mkdtemp(). The mkdtemp() function shall use the resulting
30 pathname to create the new directory as if by a call to:
31 mkdir(pathname, S_IRWXU)
34 The mkstemp() function shall create a regular file with a unique name
36 derived from template and return a file descriptor for the file open
37 for reading and writing. The application shall ensure that the string
38 provided in template is a pathname ending with at least six trailing
39 'X' characters. The mkstemp() function shall modify the contents of
40 template by replacing six or more 'X' characters at the end of the
41 pathname with the same number of characters from the portable filename
42 character set. The characters shall be chosen such that the resulting
43 pathname does not duplicate the name of an existing file at the time of
44 the call to mkstemp(). The mkstemp() function shall use the resulting
45 pathname to create the file, and obtain a file descriptor for it, as if
46 by a call to:
47 open(pathname, O_RDWR|O_CREAT|O_EXCL, S_IRUSR|S_IWUSR)
50 By behaving as if the O_EXCL flag for open() is set, the function pre‐
52 vents any possible race condition between testing whether the file
53 exists and opening it for use.
54
56 Upon successful completion, the mkdtemp() function shall return the
57 value of template. Otherwise, it shall return a null pointer and shall
58 set errno to indicate the error.
59 Upon successful completion, the mkstemp() function shall return an open
61 file descriptor. Otherwise, it shall return -1 and shall set errno to
62 indicate the error.
63
65 The mkdtemp() function shall fail if:
66 EACCES Search permission is denied on a component of the path prefix,
68 or write permission is denied on the parent directory of the
69 directory to be created.
70 EINVAL The string pointed to by template does not end in "XXXXXX".
72 ELOOP A loop exists in symbolic links encountered during resolution of
74 the path of the directory to be created.
75 EMLINK The link count of the parent directory would exceed {LINK_MAX}.
77 ENAMETOOLONG
79 The length of a component of a pathname is longer than
80 {NAME_MAX}.
81 ENOENT A component of the path prefix specified by the template argu‐
83 ment does not name an existing directory.
84 ENOSPC The file system does not contain enough space to hold the con‐
86 tents of the new directory or to extend the parent directory of
87 the new directory.
88 ENOTDIR
90 A component of the path prefix names an existing file that is
91 neither a directory nor a symbolic link to a directory.
92 EROFS The parent directory resides on a read-only file system.
94 The mkdtemp() function may fail if:
96 ELOOP More than {SYMLOOP_MAX} symbolic links were encountered during
98 resolution of the path of the directory to be created.
99 ENAMETOOLONG
101 The length of a pathname exceeds {PATH_MAX}, or pathname resolu‐
102 tion of a symbolic link produced an intermediate result with a
103 length that exceeds {PATH_MAX}.
104 The error conditions for the mkstemp() function are defined in open().
106 The following sections are informative.
108
110 Generating a Pathname
111 The following example creates a file with a 10-character name beginning
112 with the characters "file" and opens the file for reading and writing.
113 The value returned as the value of fd is a file descriptor that identi‐
114 fies the file.
115 #include <stdlib.h>
118 ...
119 char template[] = "/tmp/fileXXXXXX";
120 int fd;
121 fd = mkstemp(template);
123
125 It is possible to run out of letters.
126 Portable applications should pass exactly six trailing 'X's in the tem‐
128 plate and no more; implementations may treat any additional trailing
129 'X's as either a fixed or replaceable part of the template. To be sure
130 of only passing six, a fixed string of at least one non-'X' character
131 should precede the six 'X's.
132 Since 'X' is in the portable filename character set, some of the
134 replacement characters can be 'X's, leaving part (or even all) of the
135 template effectively unchanged.
136
138 None.
139
141 None.
142
144 getpid(), mkdir(), open(), tmpfile(), tmpnam()
145 The Base Definitions volume of POSIX.1‐2017, <stdlib.h>
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149 Portions of this text are reprinted and reproduced in electronic form
150 from IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
151 table Operating System Interface (POSIX), The Open Group Base Specifi‐
152 cations Issue 7, 2018 Edition, Copyright (C) 2018 by the Institute of
153 Electrical and Electronics Engineers, Inc and The Open Group. In the
154 event of any discrepancy between this version and the original IEEE and
155 The Open Group Standard, the original IEEE and The Open Group Standard
156 is the referee document. The original Standard can be obtained online
157 at http://www.opengroup.org/unix/online.html .
158 Any typographical or formatting errors that appear in this page are
160 most likely to have been introduced during the conversion of the source
161 files to man page format. To report such errors, see https://www.ker‐
162 nel.org/doc/man-pages/reporting_bugs.html .
163IEEE/The Open Group 2017 MKDTEMP(3P)