fdopen - Assign a file pointer to a file descriptor

Definition

#include <stdio.h> FILE *fdopen(int fd, const char *mode); fdopen assigns a file pointer to a file (with file descriptor fd) that has already been opened with open/open64 or creat/creat64. Following an fdopen call, the file may also be processed with functions from the standard I/O library (fread, fputc, fprintf etc.).

Parameters  int fd

	File descriptor that was assigned by a creat/creat64 or open/open64 call. const char *mode String which specifies the access mode (see description under fopen/fopen64). This parameter is not evaluated, i.e. the file retains the original access mode that was specified for open/open64 or creat/creat64. In other words, the access mode cannot be changed with fdopen. The optional additional specifications in the mode parameter are not evaluated either.
Return val.	File pointer to the assigned FILE structure if successful.
Note	If errors occur, e.g. due to an invalid file descriptor, fdopen returns neither a defined result nor an error message. The program does not abort either!

Example

The following program opens the file fname for elementary as well as standard input/output operations. #include <stdio.h> #include <stdlib.h> FILE *fp; int fd; char buf[10]; int c; int main(void) { int n; /* deal with the file descriptor first */ if((fd = open("fname",2)) < 0) { perror("open"); exit(1); } if((n = read(fd,buf,10)) > 0) write(1,buf,n); /* link file pointer with file descriptor */ fp = fdopen(fd,"w"); while((c = getchar()) != EOF) putc(c,fp); fclose(fp); return 0; }

See also

creat, creat64, fclose, fseek, fseek64, fopen, fopen64, freopen, freopen64, open, open64