Databases
StackOverflow2013
Postsdbo
POHow do I tell wc to stop reading?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow do I tell wc to stop reading?
    primarykey
    data
    text
    <p>I have a program that <code>fork()</code>s a new process and then overwrites that new process's <code>stdin</code> with my file descriptor pipe <code>fd</code>. In this process, I then use <code>execvp()</code> to execute <code>wc</code> and it should read its input from the parent. In the parent, I then write to the write end of the pipe and when done writing, close the pipe.</p> <p>The problem is that <code>wc</code> is still expecting input and des not exit.<br> Usually, I can stop <code>wc</code> by typing <kbd>CTRL</kbd><kbd>D</kbd> but I can't seem to send that signal in C/C++.</p> <p>How do I tell <code>wc</code> to stop reading?</p> <p><strong>EDIT</strong>: I did follow the pipe/fork/dup/exec idiom (I think that's what it's called.)<br> The streaming works with other programs that need input, its just that <code>wc</code> needs the special <code>EOF</code> to stop reading.</p> <pre><code>int in_fd[2]; //parent-child setup pipe(in_fd); child = fork(); if(child == 0) { close(in_fd[1]); dup2(in_fd[0], 0); close(in_fd[0]); execvp(cmdArg[0], cmdArg); } else { close(in_fd[0]); in_pid = fork_in_proc(); close(in_fd[1]); } //writing function pid_t fork_in_proc() { string line; pid_t in_pid; if((in_pid = fork()) == 0) { close(in_fd[0]); ifstream file(stream_file[STREAM_IN].c_str(), ios_base::in); if (file.bad()) { cerr &lt;&lt; "File read error\n"; return 1; } while(file.good()) { getline(file, line); if(file.good()) { write(in_fd[1], line.c_str(), line.length()); } } int end = 3; write(in_fd[1], &amp;end, sizeof(end)); file.close(); close(in_fd[1]); cout &lt;&lt; "PIPE IN" &lt;&lt; endl; exit(0); } else { return in_pid; } } </code></pre> <p>Sorry if the code seems a little disjointed. I had to pull it together from around the file.</p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USMorten Kristensen
    1. USchustar
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow do I tell wc to stop reading?
      1. This table or related slice is empty.
      1. VTUpMod
    2. VO
      singulars
      1. POHow do I tell wc to stop reading?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POHow do I tell wc to stop reading?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COCan you show us some code?
      singulars
      1. POHow do I tell wc to stop reading?
      1. USSome programmer dude
    2. COCTRL+D doesn't send a signal but makes whatever is reading from the terminal read EOF.
      singulars
      1. POHow do I tell wc to stop reading?
      1. USThiefMaster
    3. CO@JoachimPileborg I have added some code.
      singulars
      1. POHow do I tell wc to stop reading?
      1. USchustar
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload