From 82ba818ff456bcd6d56a06226e3f27e98fbb55c3 Mon Sep 17 00:00:00 2001 From: Craig Jennings Date: Thu, 14 Aug 2025 22:58:58 -0500 Subject: removing all downloaded devdocs files --- devdocs/c/io%2Fsetvbuf.html | 85 --------------------------------------------- 1 file changed, 85 deletions(-) delete mode 100644 devdocs/c/io%2Fsetvbuf.html (limited to 'devdocs/c/io%2Fsetvbuf.html') diff --git a/devdocs/c/io%2Fsetvbuf.html b/devdocs/c/io%2Fsetvbuf.html deleted file mode 100644 index 25309406..00000000 --- a/devdocs/c/io%2Fsetvbuf.html +++ /dev/null @@ -1,85 +0,0 @@ -

setvbuf

Defined in header <stdio.h> 
int setvbuf( FILE *         stream, char *         buffer, 
-             int mode, size_t size );
-		 (until C99) 
int setvbuf( FILE *restrict stream, char *restrict buffer, 
-             int mode, size_t size );
-		 (since C99) 
#define _IOFBF     /*unspecified*/
-#define _IOLBF     /*unspecified*/
-#define _IONBF     /*unspecified*/
-

Changes the buffering mode of the given file stream stream as indicated by the argument mode. In addition,

-

Parameters

- - - - -
stream - the file stream to set the buffer to
buffer - pointer to a buffer for the stream to use or null pointer to change size and mode only
mode - buffering mode to use. It can be one of the following values: - - - -
_IOFBF full buffering
_IOLBF line buffering
_IONBF no buffering
size - size of the buffer

Return value

​0​ on success or nonzero on failure.

-

Notes

This function may only be used after stream has been associated with an open file, but before any other operation (other than a failed call to setbuf/setvbuf).

-

Not all size bytes will necessarily be used for buffering: the actual buffer size is usually rounded down to a multiple of 2, a multiple of page size, etc.

-

On many implementations, line buffering is only available for terminal input streams.

-

A common error is setting the buffer of stdin or stdout to an array whose lifetime ends before the program terminates:

-
int main(void) {
-    char buf[BUFSIZ];
-    setbuf(stdin, buf);
-} // lifetime of buf ends, undefined behavior

The default buffer size BUFSIZ is expected to be the most efficient buffer size for file I/O on the implementation, but POSIX fstat often provides a better estimate.

-

Example

-

One use case for changing buffer size is when a better size is known. (This example uses some POSIX function, e.g. fileno. See also SO: #1 and #2).

-
// Make some POSIX functions, such as `int fileno(FILE*)`, visible:
-#define _POSIX_SOURCE
- 
-#include <stdio.h>
-#include <stdlib.h>
-#include <sys/stat.h>
- 
-int main(void)
-{
-    FILE* fp = fopen("/tmp/test.txt", "w+");
-    if (fp == NULL)
-    {
-        perror("fopen");
-        return EXIT_FAILURE;
-    }
- 
-    struct stat stats;
-    if (fstat(fileno(fp), &stats) == -1) // POSIX only
-    {
-        perror("fstat");
-        return EXIT_FAILURE;
-    }
- 
-    printf("BUFSIZ is %d, but optimal block size is %ld\n", BUFSIZ, stats.st_blksize);
-    if (setvbuf(fp, NULL, _IOFBF, stats.st_blksize) != 0)
-    {
-        perror("setvbuf failed"); // POSIX version sets errno
-        return EXIT_FAILURE;
-    }
- 
-    int ch;
-    while((ch=fgetc(fp)) != EOF); // read entire file: use truss/strace to
-                                  // observe the read(2) syscalls used
- 
-    fclose(fp);
-    return EXIT_SUCCESS;
-}

Possible output:

-
BUFSIZ is 8192, but optimal block size is 65536

References

See also

- -
sets the buffer for a file stream
(function)
C++ documentation for setvbuf
-

- © cppreference.com
Licensed under the Creative Commons Attribution-ShareAlike Unported License v3.0.
- https://en.cppreference.com/w/c/io/setvbuf -

-
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