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Top Forums Programming what would happen if a process wrote to its own stdin? Post 302302042 by c_d on Sunday 29th of March 2009 10:56:38 PM
Old 03-29-2009
Quote:
Originally Posted by Perderabo
It wrote to stdin, aka file descriptor 0. You can add:
close(1);
close(2);
in front of your "if" statement to help prove it.

In this case, the shell opened /dev/tty for reading and writing and made all three initial fd's point to it.

Try:
echo hello > file
./a.out < file
echo who knows | ./a.out

i tried the exercise you suggested on
Code:
#include<unistd.h>
#include<fcntl.h>

int main()
{

    close(STDOUT_FILENO);
    close(STDERR_FILENO);
    if((write(STDIN_FILENO,"arrgh!",6))==-1)
    {
        perror("error writing to file");
    }    

}

i get no output or error whatsoever
but when i perform the same exercise on my original code

i get
Code:
[c_d@localhost C scratchpad]$ ./a.out <file
error writing to file: Bad file descriptor
[c_d@localhost C scratchpad]$ echo watup | ./a.out
error writing to file: Bad file descriptor

Quote:
In this case, the shell opened /dev/tty for reading and writing and made all three initial fd's point to it.
i wanted to see that...but i m not able to make fcntl() work...
Code:
#include<unistd.h>
#include<fcntl.h>
#include<stdlib.h>

int main()
{
    int x=2,file,fd;
    
    if((file=open("fdvals",O_RDWR))==-1)
    {
        perror("error opening fdvals");
    }
    fd=fcntl(file,F_GETFD,0);
    printf("fd=%d",fd);
    fd=fcntl(STDOUT_FILENO,F_GETFD,0);
    printf("fd=%d",fd);
}

it tells fd=0fd=0 Smilie
 

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GIT-NAME-REV(1) 						    Git Manual							   GIT-NAME-REV(1)

NAME
git-name-rev - Find symbolic names for given revs SYNOPSIS
git name-rev [--tags] [--refs=<pattern>] ( --all | --stdin | <commit-ish>... ) DESCRIPTION
Finds symbolic names suitable for human digestion for revisions given in any format parsable by git rev-parse. OPTIONS
--tags Do not use branch names, but only tags to name the commits --refs=<pattern> Only use refs whose names match a given shell pattern. The pattern can be one of branch name, tag name or fully qualified ref name. --all List all commits reachable from all refs --stdin Transform stdin by substituting all the 40-character SHA-1 hexes (say $hex) with "$hex ($rev_name)". When used with --name-only, substitute with "$rev_name", omitting $hex altogether. Intended for the scripter's use. --name-only Instead of printing both the SHA-1 and the name, print only the name. If given with --tags the usual tag prefix of "tags/" is also omitted from the name, matching the output of git-describe more closely. --no-undefined Die with error code != 0 when a reference is undefined, instead of printing undefined. --always Show uniquely abbreviated commit object as fallback. EXAMPLE
Given a commit, find out where it is relative to the local refs. Say somebody wrote you about that fantastic commit 33db5f4d9027a10e477ccf054b2c1ab94f74c85a. Of course, you look into the commit, but that only tells you what happened, but not the context. Enter git name-rev: % git name-rev 33db5f4d9027a10e477ccf054b2c1ab94f74c85a 33db5f4d9027a10e477ccf054b2c1ab94f74c85a tags/v0.99~940 Now you are wiser, because you know that it happened 940 revisions before v0.99. Another nice thing you can do is: % git log | git name-rev --stdin GIT
Part of the git(1) suite Git 1.8.5.3 01/14/2014 GIT-NAME-REV(1)
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