hi,
how does a program know whether some data are available from stdin?
I would like to make a program which could read its data from stdin
and _if_there_is_nothing_at_stdin_ from a file which name is given
as an argument. If there is nothing in stdin and no filename is given as
argument,... (2 Replies)
hello all,
I need to create a password change utility for a database. I need to gather at the command line the username, password and database sid. I have the program currently doing this. What I would like to do is not have the new password appear on the screen when I do my read command.... (2 Replies)
Howdie everyone...
I have a shell script RemoveFiles.sh
Inside this file, it only has two commands as below:
rm -f ../../reportToday/temp/*
rm -f ../../report/*
My problem is that when i execute this script, nothing happened. Files remained unremoved. I don't see any error message as it... (2 Replies)
can you redirect STDIN with command arguments?
I have tried this approach:
# ./script -option <argument1> <argument2> 0<$2
# $2: ambiguous redirect
Is this possible? (4 Replies)
Hi,
Program A: uses pipe()
I am able to read the stdout of PROGAM B (stdout got through system() command) into PROGRAM A using:
* child
-> dup2(fd, STDOUT_FILENO);
-> execl("/path/PROGRAM B", "PROGRAM B", NULL);
* parent
-> char line;
-> read(fd, line, 100);
Question:
---------... (1 Reply)
Hi,
Program A: uses pipe()
I am able to read the stdout of PROGAM B (stdout got through system() command) into PROGRAM A using:
* child
-> dup2(fd, STDOUT_FILENO);
-> execl("/path/PROGRAM B", "PROGRAM B", NULL);
* parent
-> char line;
-> read(fd, line, 100);
Question:
---------... (3 Replies)
When a process fork(), the child share the same file descriptors as his father. Thus, they share the same stdin. Quick and dirty exemple below (sorry for the ugly gets() call) :
#include <stdio.h>
#include <unistd.h>
int main()
{
char buf;
if (fork()) { /*parent */
... (1 Reply)
Bonjour,
Mon application en C sous linux tourne en redirigeant stdin vers un fichier.
Exemple; $appli1 <file1.
PB: Je voudrais temporairement redonner la main au user sur le clavier.
Alors je pensais ajouter system("appli2"); dans appli1.
Dans son main() , appli2() fait seulement un... (1 Reply)
Hi,
I has the following command in the script. This command works fine if I execute on command prompt. If I run the script, this is not working as expected (deleting CR).
tr -d "\015" < ${FilePath}/${FileName} > ${FilePath}/${File_Prefix}.csv
I could not figure out whats... (6 Replies)
hi all. and sorry for the random question, but this sparkled a raging flame-war at work and i want more points of view
situation
a router, with linux of some sort,
dhcp client requesting for ip in wan1 (as usual with wan ports)
dhcp server listening in lan1, and assigning ip (as usual... (9 Replies)
Discussion started by: broli
9 Replies
LEARN ABOUT REDHAT
setbuf
SETBUF(3) Linux Programmer's Manual SETBUF(3)NAME
setbuf, setbuffer, setlinebuf, setvbuf - stream buffering operations
SYNOPSIS
#include <stdio.h>
void setbuf(FILE *stream, char *buf);
void setbuffer(FILE *stream, char *buf, size_tsize);
void setlinebuf(FILE *stream);
int setvbuf(FILE *stream, char *buf, int mode , 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 output or input is read from any stream attached to a terminal
device (typically stdin). The function fflush(3) may be used to force the block out early. (See fclose(3).) Normally all files are block
buffered. When the first I/O operation occurs on a file, malloc(3) is called, and a buffer is obtained. If a stream refers to a terminal
(as stdout normally does) it is line buffered. The standard error stream stderr is always unbuffered by default.
The setvbuf function may be used on any open stream to change its buffer. The mode parameter must be one of the following three macros:
_IONBF unbuffered
_IOLBF line buffered
_IOFBF fully buffered
Except for unbuffered files, the buf argument should point to a buffer at least size bytes long; this buffer will be used instead of the
current buffer. If the argument buf is NULL, only the mode is affected; a new buffer will be allocated on the next read or write opera-
tion. The setvbuf function may only be used after opening a stream and before any other operations have been performed on it.
The other three calls are, in effect, simply aliases for calls to setvbuf. The setbuf function is exactly equivalent to the call
setvbuf(stream, buf, buf ? _IOFBF : _IONBF, BUFSIZ);
The setbuffer function is the same, except that the size of the buffer is up to the caller, rather than being determined by the default
BUFSIZ. The setlinebuf function is exactly equivalent to the call:
setvbuf(stream, (char *)NULL, _IOLBF, 0);
RETURN VALUE
The function setvbuf returns 0 on success. It can return any value on failure, but returns nonzero when mode is invalid or the request
cannot be honoured. It may set errno on failure. The other functions are void.
CONFORMING TO
The setbuf and setvbuf functions conform to ANSI X3.159-1989 (``ANSI C'').
BUGS
The setbuffer and setlinebuf functions are not portable to versions of BSD before 4.2BSD, and are available under Linux since libc 4.5.21.
On 4.2BSD and 4.3BSD systems, setbuf always uses a suboptimal buffer size and should be avoided.
You must make sure that both buf and the space it points to still exist by the time stream is closed, which also happens at program termi-
nation.
For example, the following is illegal:
#include <stdio.h>
int main()
{
char buf[BUFSIZ];
setbuf(stdin, buf);
printf("Hello, world!
");
return 0;
}
SEE ALSO fclose(3), fflush(3), fopen(3), fread(3), malloc(3), printf(3), puts(3)Linux 2001-06-09 SETBUF(3)