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setbuf(3c) [opensolaris man page]

setbuf(3C)						   Standard C Library Functions 						setbuf(3C)

NAME
setbuf, setvbuf - assign buffering to a stream SYNOPSIS
#include <stdio.h> void setbuf(FILE *stream, char *buf); int setvbuf(FILE *stream, char *buf, int type, size_t size); DESCRIPTION
The setbuf() function may be used after the stream pointed to by stream (see Intro(3)) is opened but before it is read or written. It causes the array pointed to by buf to be used instead of an automatically allocated buffer. If buf is the null pointer, input/output will be completely unbuffered. The constant BUFSIZ, defined in the <stdio.h> header, indicates the size of the array pointed to by buf. The setvbuf() function may be used after a stream is opened but before it is read or written. The type argument determines how stream will be buffered. Legal values for type (defined in <stdio.h>) are: _IOFBF Input/output to be fully buffered. _IOLBF Output to be line buffered; the buffer will be flushed when a NEWLINE is written, the buffer is full, or input is requested. _IONBF Input/output to be completely unbuffered. If buf is not the null pointer, the array it points to will be used for buffering, instead of an automatically allocated buffer. The size argument specifies the size of the buffer to be used. If input/output is unbuffered, buf and size are ignored. For a further discussion of buffering, see stdio(3C). RETURN VALUES
If an illegal value for type is provided, setvbuf() returns a non-zero value. Otherwise, it returns 0. USAGE
A common source of error is allocating buffer space as an "automatic" variable in a code block, and then failing to close the stream in the same block. When using setbuf(), buf should always be sized using BUFSIZ. If the array pointed to by buf is larger than BUFSIZ, a portion of buf will not be used. If buf is smaller than BUFSIZ, other memory may be unexpectedly overwritten. Parts of buf will be used for internal bookkeeping of the stream and, therefore, buf will contain less than size bytes when full. It is recommended that stdio(3C) be used to handle buffer allocation when using setvbuf(). ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Interface Stability |Standard | +-----------------------------+-----------------------------+ |MT-Level |MT-Safe | +-----------------------------+-----------------------------+ SEE ALSO
fopen(3C), getc(3C), malloc(3C), putc(3C), stdio(3C), attributes(5), standards(5) SunOS 5.11 14 Aug 2002 setbuf(3C)

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SETBUF(3)						     Library Functions Manual							 SETBUF(3)

NAME
setbuf, setvbuf - assign buffering to a stream SYNOPSIS
#include <stdio.h> int setbuf(FILE *stream, char *buf) int setvbuf(FILE *stream, char *buf, int type, size_t size) DESCRIPTION
The three types of buffering available are unbuffered, block buffered, and line buffered. When an output stream is unbuffered, information appears on the destination file or terminal as soon as written; when it is block buffered many characters are saved up and written as a block; when it is line buffered characters are saved up until a newline is encountered or input is read from stdin. Fflush (see fclose(3)) may be used to force the block out early. Normally all files are block buffered. A buffer is obtained from malloc(3) upon the first getc or putc(3) on the file. If the standard stream stdout refers to a terminal it is line buffered. The standard stream stderr is always unbuffered. Setbuf is used after a stream has been opened but before it is read or written. The character array buf is used instead of an automati- cally allocated buffer. If buf is the constant pointer NULL, input/output will be completely unbuffered. A manifest constant BUFSIZ tells how big an array is needed: char buf[BUFSIZ]; Setvbuf, an alternate form of setbuf, is used after a stream has been opened but before it is read or written. It has three uses, depend- ing on the value of the type argument: setvbuf(stream, buf, _IOFBF, size) Causes input/output to be fully buffered using the character array buf whose size is determined by the size argument. If buf is the constant pointer NULL, then an automatically allocated buffer will be used. setvbuf(stream, buf, _IOLBF, size) Like above, except that output will be line buffered, i.e. the buffer will be flushed when a newline is written, the buffer is full, or input is requested. setvbuf(stream, buf, _IONBF, size) Causes input/output to be completely unbuffered. Buf and size are ignored. A file can be changed between unbuffered, line buffered, or block buffered by using freopen (see fopen(3)) followed by the appropriate setvbuf call. SEE ALSO
fopen(3), getc(3), putc(3), malloc(3), fclose(3), puts(3), printf(3), fread(3). 4th Berkeley Distribution May 12, 1986 SETBUF(3)
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