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TMPFILE(3)		     Library Functions Manual		      TMPFILE(3)

NAME
     tempnam, tmpfile, tmpnam -- temporary file routines

LIBRARY
     Standard C Library (libc, -lc)

SYNOPSIS
     #include <stdio.h>

     FILE *
     tmpfile(void);

     char *
     tmpnam(char *str);

     char *
     tempnam(const char *tmpdir, const char *prefix);

DESCRIPTION
     The tmpfile() function returns a pointer to a stream associated with a file
     descriptor  returned  by  the  routine mkstemp(3).  The created file is un-
     linked before tmpfile() returns,  causing	the  file  to  be  automatically
     deleted  when  the last reference to it is closed.  The file is opened with
     the access value `w+'.  The file is created in the directory determined  by
     the  environment variable TMPDIR if set.  The default location if TMPDIR is
     not set is /tmp.

     The tmpnam() function returns a pointer to a file name, in the P_tmpdir di-
     rectory, which did not reference an existing  file  at  some  indeterminate
     point  in the past.  P_tmpdir is defined in the include file <stdio.h>.  If
     the argument str is non-NULL, the file name is copied to the buffer it ref-
     erences.  Otherwise, the file name is copied to a static buffer.  In either
     case, tmpnam() returns a pointer to the file name.

     The buffer referenced by str is expected to be at least L_tmpnam  bytes  in
     length.  L_tmpnam is defined in the include file <stdio.h>.

     The  tempnam() function is similar to tmpnam(), but provides the ability to
     specify the directory which will contain the temporary file  and  the  file
     name prefix.

     The   environment	variable  TMPDIR  (if  set),  the  argument  tmpdir  (if
     non-NULL), the directory P_tmpdir, and the directory /tmp are tried, in the
     listed order, as directories in which to store the temporary file.

     The argument prefix, if non-NULL, is used to specify a  file  name  prefix,
     which will be the first part of the created file name.  The tempnam() func-
     tion allocates memory in which to store the file name; the returned pointer
     may be used as a subsequent argument to free(3).

RETURN VALUES
     The tmpfile() function returns a pointer to an open file stream on success,
     and a NULL pointer on error.

     The  tmpnam()  and  tempfile() functions return a pointer to a file name on
     success, and a NULL pointer on error.

ENVIRONMENT
     TMPDIR  [tempnam() and tmpfile() only] If set, the directory in  which  the
	     temporary	file  is  stored.   TMPDIR  is ignored for processes for
	     which issetugid(2) is true.

COMPATIBILITY
     These interfaces are provided from System V and ANSI compatibility only.

     Most historic implementations of these functions  provide	only  a  limited
     number of possible temporary file names (usually 26) before file names will
     start  being recycled.  System V implementations of these functions (and of
     mktemp(3)) use the access(2) system call to determine whether  or	not  the
     temporary	file  may be created.  This has obvious ramifications for setuid
     or setgid programs, complicating the portable use of  these  interfaces  in
     such programs.

     The  tmpfile() interface should not be used in software expected to be used
     on other systems if there is any possibility that the user  does  not  wish
     the temporary file to be publicly readable and writable.

ERRORS
     The  tmpfile()  function may fail and set the global variable errno for any
     of the errors specified for the library functions fdopen(3) or mkstemp(3).

     The tmpnam() function may fail and set errno for any of the  errors  speci-
     fied for the library function mktemp(3).

     The  tempnam() function may fail and set errno for any of the errors speci-
     fied for the library functions malloc(3) or mktemp(3).

SEE ALSO
     mkstemp(3), mktemp(3)

STANDARDS
     The  tmpfile()  and  tmpnam()  functions  conform	to   ISO/IEC   9899:1990
     ("ISO C90").

SECURITY CONSIDERATIONS
     The  tmpnam()  and  tempnam() functions are susceptible to a race condition
     occurring between the selection of the file name and the  creation  of  the
     file, which allows malicious users to potentially overwrite arbitrary files
     in  the system, depending on the level of privilege of the running program.
     Additionally, there is no means by which file permissions may be specified.
     It is strongly suggested that mkstemp(3) be used in place	of  these  func-
     tions.

FreeBSD 15.1			 August 7, 2020 		      TMPFILE(3)
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