tmpnam(3S) — sys5



TMPNAM(3S)      DOMAIN/IX Reference Manual (SYS5)      TMPNAM(3S)



NAME
     tmpnam, tempnam - create a name for a temporary file

USAGE
     #include <stdio.h>

     char *tmpnam (s)
     char *s;

     char *tempnam (dir, pfx)
     char *dir, *pfx;

DESCRIPTION
     These functions generate ``safe'' filenames for temporary
     files.

     Tmpnam always generates a filename using the path-prefix
     defined as Ptmpdir in the <stdio.h> header file.  If s is
     NULL, tmpnam leaves its result in an internal static area
     and returns a pointer to that area.  The next call to tmpnam
     will destroy the contents of the area.  If s is not NULL, it
     is assumed to be the address of an array of at least
     Ltmpnam bytes, where Ltmpnam is a constant defined in
     <stdio.h>; tmpnam places its result in that array and
     returns s.

     Tempnam allows the user to control the choice of a direc-
     tory.  The argument dir points to the name of the directory
     in which the file is to be created.  If dir is NULL or
     points to a string which is not a name for an appropriate
     directory, the path-prefix defined as Ptmpdir in the
     <stdio.h> header file is used.  If that directory is not
     accessible, /tmp will be used as a last resort.  This entire
     sequence can be avoided by providing an environment variable
     TMPDIR in the user's environment, whose value is the name of
     the desired temporary-file directory.

     Many applications prefer their temporary files to have cer-
     tain initial letter sequences in their names.  Use the pfx
     argument for this.  This argument may be NULL or point to a
     string of up to five characters to be used as the first few
     characters of the temporary filename.

     Tempnam uses malloc(3C) to get space for the constructed
     filename, and returns a pointer to this area.  Thus, any
     pointer value returned from tempnam may serve as an argument
     to free (see malloc(3C)).  If tempnam cannot return the
     expected result for any reason, e.g., if malloc(3C) failed,
     or none of the above mentioned attempts to find an appropri-
     ate directory was successful, a NULL pointer will be
     returned.




Printed 5/10/85                                          TMPNAM-1



TMPNAM(3S)      DOMAIN/IX Reference Manual (SYS5)      TMPNAM(3S)



NOTES
     These functions generate a different filename each time they
     are called.  However, if called more than 17,576 times in a
     single process, they will start recycling previously used
     names.

     Between the time a filename is created and the file is
     opened, it is possible for some other process to create a
     file with the same name.  This is not as likely if the other
     process is using these functions or mktemp, and the file
     names are chosen so as to render duplication by other means
     unlikely.

     Files created using these functions and either fopen(3S) or
     creat(2) are temporary only in the sense that they reside in
     a directory intended for temporary use, and their names are
     unique.  It is the user's responsibility to use unlink(2) to
     remove the file when its use is ended.

RELATED INFORMATION
     creat(2), unlink(2), fopen(3S), malloc(3C), mktemp(3C),
     tmpfile(3S)

































TMPNAM-2                                          Printed 5/10/85

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