Page 158 - C-Language

Chapter 22: Files and I/O streams

Syntax

• #include <stdio.h> /* Include this to use any of the following sections */
• FILE *fopen(const char *path, const char *mode); /* Open a stream on the file at path with
the specified mode */
• FILE *freopen(const char *path, const char *mode, FILE *stream); /* Re-open an existing
stream on the file at path with the specified mode */
• int fclose(FILE *stream); /* Close an opened stream */
• size_t fread(void *ptr, size_t size, size_t nmemb, FILE *stream); /* Read at most nmemb
elements of size bytes each from the stream and write them in ptr. Returns the number of
read elements. */
• size_t fwrite(const void *ptr, size_t size, size_t nmemb, FILE *stream); /* Write nmemb
elements of size bytes each from ptr to the stream. Returns the number of written elements.
*/
• int fseek(FILE *stream, long offset, int whence); /* Set the cursor of the stream to offset,
relative to the offset told by whence, and returns 0 if it succeeded. */
• long ftell(FILE *stream); /* Return the offset of the current cursor position from the beginning
of the stream. */
• void rewind(FILE *stream); /* Set the cursor position to the beginning of the file. */
• int fprintf(FILE *fout, const char *fmt, ...); /* Writes printf format string on fout */
• FILE *stdin; /* Standard input stream */
• FILE *stdout; /* Standard output stream */
• FILE *stderr; /* Standard error stream */

Parameters

Parameter Details

const char A string describing the opening mode of the file-backed stream. See remarks
*mode for possible values.

Can be SEEK_SET to set from the beginning of the file, SEEK_END to set from its
int whence end, or SEEK_CUR to set relative to the current cursor value. Note: SEEK_END is
non-portable.

Remarks

Mode strings:

Mode strings in fopen() and freopen() can be one of those values:

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