tmpfile() — Create temporary file

Standards

Standards / Extensions	C or C++	Dependencies
ISO C POSIX.1 XPG4 XPG4.2 C99 Single UNIX Specification, Version 3	both

Format

#include <stdio.h>

FILE *tmpfile(void);

General description

Creates a temporary binary file. It opens the temporary file in wb+ mode. The file is automatically removed when it is closed or when the program is terminated.

Note: When the tmpfile() function is issued from multiple tasks within one address space, the temporary file names may not be unique. The execution of the tmpfile() function concurrently within one address space will result in errors. For example, an open will fail because the file is already open.

Returned value

If successful, tmpfile() returns a pointer to the stream associated with the file created.

If tmpfile() cannot open the file, it returns a NULL pointer. On normal termination (exit()), these temporary files are removed. On abnormal termination, an effort is made to remove these files.

Returned value for POSIX C

When the calling application is a z/OS® UNIX program, the temporary file is created in the hierarchical file system. The file is created in the directory referred to by the TMPDIR environment variable, or '/tmp' if TMPDIR is not defined.

Special behavior for XPG4:The following are the possible values of errno:

Error Code: Description
EINTR: A signal was caught during tmpfile().
EMFILE: OPEN_MAX file descriptors are currently open in the calling process.
: {FOPEN_MAX} streams are currently open in the calling process.
ENFILE: The maximum allowable number of files is currently open in the system.
ENOMEM: Insufficient storage space is available.
ENOSPC: The directory or file system which would contain the new file cannot be expanded.

Example

CELEBT13

⁄* CELEBT13                                      

   This example creates a temporary file and if successful,                     
   writes tmpstring to it.                                                      
   At program termination, the file is removed.                                 

 *⁄                                                                             
#include <stdio.h>                                                              
                                                                                
int main(void) {                                                                
   FILE *stream;                                                                
   char tmpstring[ ] = "This string will be written";                           
                                                                                
{                                                                               
   if((stream = tmpfile( )) == NULL)                                            
      printf("Cannot make a temporary file\n");                                 
   else                                                                         
      fprintf(stream, "%s", tmpstring);                                         
}                                                                               
}