I've run into a snag in a program of mine where part of what I entered in at the start of run-time, instead of the current value within printf() is being printed out.
After failing with fflush() and setbuf(), I tried the following approach
however this has not improved things (even with replacing getchar() with fgetc(stdin) ).
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:... (2 Replies)
Hi everyone, first post here.
Anyone who isn't interested in the background, press pagedown :).
I sometimes need to make scripts for little things I need in the infrastructure at the company I work at. Currently I am trying to make a wrapper script for a proprietary image-deployment program.... (2 Replies)
Hi,
i know how to
a) redirect stdout and stderr to one file,
b) and write to two files concurrently with same output using tee command
Now, i want to do both the above together.
I have a script and it should write both stdout and stderr in one file and also write the same content to... (8 Replies)
Hi,
I am working on a project where I have to generate and execute nasm code on-the-fly. I generate the code in a file program.asm and then execute it.This output is to stdout which i redirect to an output file which i read back to compare results:
system("nasm -f elf program.asm >... (5 Replies)
All,
Ok...so I know I *should* be able to control a process's stdin and stdout from the parent by creating pipes and then dup'ing them in the child. And, this works with all "normal" programs that I've tried. Unfortunately, I want to intercept the stdin/out of the scp application and it seems... (9 Replies)
Hi,
i am using the below program to read from the standard input or to write to standard out put.
i know that using highlevel functions this can be done better than what i have done here.
i just want to know is there any other method by which i find the exact number of characters ( this... (3 Replies)
I want to differentiate the STDOUT and STDERR messages in my terminal .
If a script or command is printing a message in terminal I want to differentiate by colors,
Is it possible ?
Example:
$date
Wed Jul 27 12:36:50 IST 2011
$datee
bash: datee: command not found
$alias ls
alias... (2 Replies)
Well.. let's say i need to write a pretty simple script.
In my script i have 2 variables which can have value of 0 or 1.
$VERBOSE
$LOG
I need to implement these cases:
($VERBOSE = 0 && $LOG = 0) => ONLY ERROR output (STDERR to console && STDOUT to /dev/null)
($VERBOSE = 1... (5 Replies)
Discussion started by: Marmz
5 Replies
LEARN ABOUT CENTOS
stdout
STDIN(3) Linux Programmer's Manual STDIN(3)NAME
stdin, stdout, stderr - standard I/O streams
SYNOPSIS
#include <stdio.h>
extern FILE *stdin;
extern FILE *stdout;
extern FILE *stderr;
DESCRIPTION
Under normal circumstances every UNIX program has three streams opened for it when it starts up, one for input, one for output, and one for
printing diagnostic or error messages. These are typically attached to the user's terminal (see tty(4) but might instead refer to files or
other devices, depending on what the parent process chose to set up. (See also the "Redirection" section of sh(1).)
The input stream is referred to as "standard input"; the output stream is referred to as "standard output"; and the error stream is
referred to as "standard error". These terms are abbreviated to form the symbols used to refer to these files, namely stdin, stdout, and
stderr.
Each of these symbols is a stdio(3) macro of type pointer to FILE, and can be used with functions like fprintf(3) or fread(3).
Since FILEs are a buffering wrapper around UNIX file descriptors, the same underlying files may also be accessed using the raw UNIX file
interface, that is, the functions like read(2) and lseek(2).
On program startup, the integer file descriptors associated with the streams stdin, stdout, and stderr are 0, 1, and 2, respectively. The
preprocessor symbols STDIN_FILENO, STDOUT_FILENO, and STDERR_FILENO are defined with these values in <unistd.h>. (Applying freopen(3) to
one of these streams can change the file descriptor number associated with the stream.)
Note that mixing use of FILEs and raw file descriptors can produce unexpected results and should generally be avoided. (For the masochis-
tic among you: POSIX.1, section 8.2.3, describes in detail how this interaction is supposed to work.) A general rule is that file descrip-
tors are handled in the kernel, while stdio is just a library. This means for example, that after an exec(3), the child inherits all open
file descriptors, but all old streams have become inaccessible.
Since the symbols stdin, stdout, and stderr are specified to be macros, assigning to them is nonportable. The standard streams can be made
to refer to different files with help of the library function freopen(3), specially introduced to make it possible to reassign stdin, std-
out, and stderr. The standard streams are closed by a call to exit(3) and by normal program termination.
CONFORMING TO
The stdin, stdout, and stderr macros conform to C89 and this standard also stipulates that these three streams shall be open at program
startup.
NOTES
The stream stderr is unbuffered. The stream stdout is line-buffered when it points to a terminal. Partial lines will not appear until
fflush(3) or exit(3) is called, or a newline is printed. This can produce unexpected results, especially with debugging output. The
buffering mode of the standard streams (or any other stream) can be changed using the setbuf(3) or setvbuf(3) call. Note that in case
stdin is associated with a terminal, there may also be input buffering in the terminal driver, entirely unrelated to stdio buffering.
(Indeed, normally terminal input is line buffered in the kernel.) This kernel input handling can be modified using calls like tcse-
tattr(3); see also stty(1), and termios(3).
SEE ALSO csh(1), sh(1), open(2), fopen(3), stdio(3)COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2008-07-14 STDIN(3)