Sponsored Content
Top Forums Programming what would happen if a process wrote to its own stdin? Post 302302522 by c_d on Tuesday 31st of March 2009 07:42:18 AM
Old 03-31-2009
Code:
#include <stdio.h>

int main(void) {
    if ( fprintf(stdin, "A") < 1 )
        perror("fprintf");
    return 0;
}

OP:
Code:
[c_d@localhost C scratchpad]$ gcc temp.c
[c_d@localhost C scratchpad]$ ./a.out 
fprintf: Bad file descriptor

so...how come now stdin becomes an invalid fd?

now when i do this
Code:
#include <stdio.h>
#include <unistd.h>

int main(void) {
    FILE *fakestdin;
    fakestdin = fdopen(STDIN_FILENO, "a+");
    if(fakestdin!=NULL)
    {
        fprintf(fakestdin, "A\n");
         perror("fakestdin");
    }
    else
          printf("fakestdin is NULL");
    return 0;    
}

OP:
Code:
[c_d@localhost C scratchpad]$ gcc temp.c
[c_d@localhost C scratchpad]$ ./a.out <temp.c
fakestdin is NULL[c_d@localhost C scratchpad]$ ./a.out 
A
fakestdin: Success
[c_d@localhost C scratchpad]$

it opens and writes to /dev/tty...

so what does this mean?

does it mean that (STDIN_FILENO) points to /dev/tty under normal conditions, but stdin does not? then where does it point to?

why did i have to open "stdin"'s fd to write to it? because i never have to open "stdout"'s fd to write to it...

Code:
#include <stdio.h>

int main(void) {
     fprintf(stdout, "HELLO!");
        perror("fprintf");
    return 0;
}

Code:
[c_d@localhost C scratchpad]$ gcc temp.c
[c_d@localhost C scratchpad]$ ./a.out 
fprintf: Success
HELLO![c_d@localhost C scratchpad]$

 

10 More Discussions You Might Find Interesting

1. UNIX for Dummies Questions & Answers

what happen when changing Hostname?

I 'm using RH 7.2 Genome in the Network Configuration I change therer are two places one for static hostname for my machine and in DNS hostname I don't know what happen when restarting my PC when connecting using dialer I can't browse the Internet also I can't use sendmail .......Server timeout... (2 Replies)
Discussion started by: atiato
2 Replies

2. Programming

Any one can tell me how this happen?

The #1 Online Store for Louis Vuitton Replicas is: http://www.opichina.com.cn. We offer Louis Vuitton Replicas and more! Whatever you call it: LV Bags, LV Replicas, Louis Vuitton Fake, Louis Vuitton Knockoffs, Louis Vuitton Bag, Louis Vuitton Purse, Louis Vuitton Wallet, Louis Vuitton Shoes,... (10 Replies)
Discussion started by: jiangyanna
10 Replies

3. UNIX for Dummies Questions & Answers

What would happen if. . .

Hi, Could someone please tell me what would happen if the following were entered into the command line: rm -i /books/*.* rm /books/* Many thanks! (3 Replies)
Discussion started by: crispy
3 Replies

4. UNIX for Advanced & Expert Users

Unix ID deleted - What happen to process

I have an unix id (AIX system) which is used to run a couple of processes. They also write some log files into a file system (that is not in the home directory of the user id, but in different location). One bad day, the id was deleted accidentally. But the home directory, files and everything... (1 Reply)
Discussion started by: cmgreat
1 Replies

5. UNIX for Dummies Questions & Answers

whats happen when we create new user

hi frndz I wanna knw exatly what happen when we create new user... which directories are created ?? which files are modified ?? thanx.... (2 Replies)
Discussion started by: luckypower
2 Replies

6. AIX

How does ITIL processing happen in AIX?

How does ITIL process is implemened in AIX? (6 Replies)
Discussion started by: AIXlearner
6 Replies

7. UNIX for Dummies Questions & Answers

What Does Happen During Boot Process? - BIOS and MBR

I'm talking about boot process in multi-boot Linux perceptive. Please tell me whether my explanation is right or wrong? If wrong, please explain. "The BIOS checks the system and loads this initial bootstrapping code into memory. This initial bootstrap code searches for an active partition... (0 Replies)
Discussion started by: f.ben.isaac
0 Replies

8. UNIX for Advanced & Expert Users

Who actually wrote Professional Linux Programming ?

Hello, Who actually wrote Professional Linux Programming of Wrox publication as there are two different sets of writers, one set consists of Jon Masters and Richard Blum and another set of writers is Neil Mathew with lots of other writers. Plz resolve it. I'm really confused. Regards.. (0 Replies)
Discussion started by: vectrum
0 Replies

9. Shell Programming and Scripting

Crontab - wrote Simple Script but i cant work out how to play it at a certain time.

Hi everyone. Silly might be silly be I'm still new to bash. I'm trying to make an Alarm Clock for in the morning using my laptop i have wrote this Simple Script but i cant work out how to play it at a certain time. #!/bin/bash cd /home/josh/Music/Bruno_Mars/Hooligans/ cvlc... (8 Replies)
Discussion started by: jtsmith90
8 Replies

10. What is on Your Mind?

Ah, the AMIGA, (another poem I wrote in 2005).

Well I wrote this in 2005 and uploaded to AMINET.as a commemoration of a machine that is still in use today. It is now 29 years since this machne came into being. Phenominal and it is still being supported- WOW! My A1200 is on 24/7 and I use it to test code developed on AMIGA emulators... ... (0 Replies)
Discussion started by: wisecracker
0 Replies
MAXDB_STMT_ERRNO(3)							 1						       MAXDB_STMT_ERRNO(3)

maxdb_stmt_errno - Returns the error code for the most recent statement call

       Procedural style

SYNOPSIS
int maxdb_stmt_errno (resource $stmt) DESCRIPTION
Object oriented style int$maxdb_stmt->errno () For the statement specified by stmt, maxdb_stmt_errno(3) returns the error code for the most recently invoked statement function that can succeed or fail. Note For possible error codes see documentation of SQLDBC: http://maxdb.sap.com/documentation/. RETURN VALUES
An error code value. Zero means no error occurred. EXAMPLES
Example #1 Object oriented style <?php /* Open a connection */ $maxdb = new maxdb("localhost", "MONA", "RED", "DEMODB"); /* check connection */ if (maxdb_connect_errno()) { printf("Connect failed: %s ", maxdb_connect_error()); exit(); } $maxdb->query("CREATE TABLE temp.mycity LIKE hotel.city"); $maxdb->query("INSERT INTO temp.mycity SELECT * FROM hotel.city"); $query = "SELECT name, zip FROM temp.mycity ORDER BY name"; if ($stmt = $maxdb->prepare($query)) { /* drop table */ $maxdb->query("DROP TABLE temp.mycity"); /* execute query */ $stmt->execute(); printf("Error: %d. ", $stmt->errno); /* close statement */ $stmt->close(); } /* close connection */ $maxdb->close(); ?> Example #2 Procedural style <?php /* Open a connection */ $link = maxdb_connect("localhost", "MONA", "RED", "DEMODB"); /* check connection */ if (maxdb_connect_errno()) { printf("Connect failed: %s ", maxdb_connect_error()); exit(); } maxdb_query($link, "CREATE TABLE temp.mycity LIKE hotel.city"); maxdb_query($link, "INSERT INTO temp.mycity SELECT * FROM hotel.city"); $query = "SELECT name, zip FROM temp.mycity ORDER BY name"; if ($stmt = maxdb_prepare($link, $query)) { /* drop table */ maxdb_query($link, "DROP TABLE temp.mycity"); /* execute query */ maxdb_stmt_execute($stmt); printf("Error: %d. ", maxdb_stmt_errno($stmt)); /* close statement */ maxdb_stmt_close($stmt); } /* close connection */ maxdb_close($link); ?> The above example will output something similar to: Warning: maxdb_stmt_execute(): -4004 POS(23) Unknown table name:MYCITY [42000] <...> Error: -4004. SEE ALSO
maxdb_stmt_error(3), maxdb_stmt_sqlstate(3). PHP Documentation Group MAXDB_STMT_ERRNO(3)
All times are GMT -4. The time now is 05:35 PM.
Unix & Linux Forums Content Copyright 1993-2022. All Rights Reserved.
Privacy Policy