mkstemp(3)

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

6       mkstemp - 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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DESCRIPTION

14       The  mkstemp() function generates a unique temporary filename from tem‐
15       plate.  The last six characters of template must be  XXXXXX  and  these
16       are  replaced with a string that makes the filename unique. The file is
17       then created with mode read/write and permissions 0666 (glibc 2.0.6 and
18       earlier),  0600  (glibc  2.0.7  and later).  Since it will be modified,
19       template must not be a string constant, but should  be  declared  as  a
20       character  array.   The  file  is  opened with the open(2) O_EXCL flag,
21       guaranteeing that when mkstemp() returns successfully we are  the  only
22       user.
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RETURN VALUE

25       On  success,  the mkstemp() function returns the file descriptor of the
26       temporary file.  On error, -1 is returned, and errno is  set  appropri‐
27       ately.
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ERRORS

30       EEXIST Could  not create a unique temporary filename.  Now the contents
31              of template are undefined.
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33       EINVAL The last six characters of template were not XXXXXX.   Now  tem‐
34              plate is unchanged.
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NOTES

37       The  old  behaviour  (creating a file with mode 0666) may be a security
38       risk, especially since other Unix flavours use 0600, and somebody might
39       overlook this detail when porting programs.
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41       More  generally,  the  POSIX  specification does not say anything about
42       file modes, so the application should make sure its umask is set appro‐
43       priately before calling mkstemp().
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CONFORMING TO

46       4.3BSD, POSIX.1-2001
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NOTE

49       The prototype is in <unistd.h> for libc4, libc5, glibc1; glibc2 follows
50       the Single Unix Specification and has the prototype in <stdlib.h>.
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