mkostemp(3)

1MKSTEMP(3)                 Linux Programmer's Manual                MKSTEMP(3)
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NAME

6       mkstemp, mkostemp - create a unique temporary file
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SYNOPSIS

9       #include <stdlib.h>
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11       int mkstemp(char *template);
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13       int mkostemp (char *template, int flags);
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15   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
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17       mkstemp(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500
18       mkostemp(): _GNU_SOURCE
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DESCRIPTION

21       The  mkstemp() function generates a unique temporary filename from tem‐
22       plate, creates and opens the file, and returns an open file  descriptor
23       for the file.
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25       The  last  six  characters  of  template must be "XXXXXX" and these are
26       replaced with a string that makes the filename unique.  Since  it  will
27       be  modified,  template  must  not  be a string constant, but should be
28       declared as a character array.
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30       The file is created with permissions 0600, that is, read plus write for
31       owner  only.   (In glibc versions 2.06 and earlier, the file is created
32       with permissions 0666, that is, read and write  for  all  users.)   The
33       returned  file  descriptor  provides  both read and write access to the
34       file.  The file is opened with the open(2)  O_EXCL  flag,  guaranteeing
35       that the caller is the process that creates the file.
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37       mkostemp()  is  like  mkstemp(),  with the difference that flags as for
38       open(2) may be specified in flags (e.g., O_APPEND, O_SYNC).
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RETURN VALUE

41       On success, these functions return the file descriptor of the temporary
42       file.  On error, -1 is returned, and errno is set appropriately.
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ERRORS

45       EEXIST Could  not create a unique temporary filename.  Now the contents
46              of template are undefined.
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48       EINVAL The last six characters of template were not XXXXXX.   Now  tem‐
49              plate is unchanged.
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51       These  functions  may  also  fail  with any of the errors described for
52       open(2).
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VERSIONS

55       mkostemp() is available since glibc 2.7.
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CONFORMING TO

58       mkstemp(): 4.3BSD, POSIX.1-2001.  mkostemp(): is a glibc extension.
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NOTES

61       The old behavior of creating a file with mode 0666 may  be  a  security
62       risk,  especially since other Unix flavors use 0600, and somebody might
63       overlook this detail when porting programs.
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65       More generally, the POSIX specification of mkstemp() does not say  any‐
66       thing  about  file  modes, so the application should make sure its file
67       mode creation mask (see umask(2)) is set appropriately  before  calling
68       mkstemp() (and mkostemp()).
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70       The  prototype  for mktemp() is in <unistd.h> for libc4, libc5, glibc1;
71       glibc2 follows POSIX.1 and has the prototype in <stdlib.h>.
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COLOPHON

77       This page is part of release 3.22 of the Linux  man-pages  project.   A
78       description  of  the project, and information about reporting bugs, can
79       be found at http://www.kernel.org/doc/man-pages/.
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83GNU                               2008-06-19                        MKSTEMP(3)