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    <p>Have a look at this <a href="http://www.cs.nmsu.edu/~jcook/Tools/pthreads/pthreads.html" rel="nofollow">http://www.cs.nmsu.edu/~jcook/Tools/pthreads/pthreads.html</a></p> <p>You propably know that a fork() produces a copy of the calling process and that this copy is (almost) identical to the original - they only differ in that fork() in the child = 1</p> <p>Try (and tell me if its working, i could not test it :)</p> <pre><code> for(i=1; i&lt;=counter; i++){ child_pid = fork(); switch(child_pid) { case -1: printf("Error occured with fork()\n"); exit(1); case 0: print_screen(i); /* Child Process */ exit(0); default: printf("...\n"); } } </code></pre> <p>EDIT: works for me</p> <p>EDIT: okay i did some testing, should rather use <code>if</code> instead of <code>case</code> (also added dirext output of file content - should remove that if file size growth ); now thats what i had as code: </p> <pre><code>#include &lt;stdio.h&gt; /* basic I/O routines. */ #include &lt;unistd.h&gt; /* define fork(), etc. */ #include &lt;sys/types.h&gt; /* define pid_t, etc. */ #include &lt;sys/wait.h&gt; /* define wait(), etc. */ #include &lt;signal.h&gt; /* define signal(), etc. */ #include &lt;pthread.h&gt; #include &lt;time.h&gt; void print_screen(int i); int counter=0; int main(int argc, char* argv[]) { FILE* fptr; fptr = fopen("sample.txt","w"); int counter = atoi(argv[1]); int i,k; int temp; pid_t child_pid; int child_status; char array[counter]; srand ( time(NULL) ); for(i=0; i&lt;counter; i++){ temp = rand()%4; if( temp==0 ) { fprintf(fptr,"A\n"); printf("A\n"); array[i]='A'; } else if( temp==1 ) { fprintf(fptr,"C\n"); printf("C\n"); array[i]='C'; } else if( temp==2 ) { fprintf(fptr,"G\n"); printf("G\n"); array[i]='G'; } else if( temp==3 ) { fprintf(fptr,"T\n"); printf("T\n"); array[i]='T'; } } fclose(fptr); for(i=1; i&lt;=counter; i++){ child_pid = fork(); if (child_pid == -1){ printf("Error occured with fork()\n"); exit(-1); } else if (child_pid == 0){ print_screen(i); exit(0); } else{ printf("something \n"); } } wait(&amp;child_status); execl("/usr/bin/killall","killall","tail",(char *) 0); return 0; } void print_screen(int i){ char* str; FILE* fptr; fptr=fopen("sample.txt","r"); fseek(fptr,i,SEEK_SET); fscanf(fptr,"%s",str); printf("Process Number %d, Character = %s\n",i,str); sleep(1); fclose(fptr); return; } </code></pre> <p>it doesnt work correct (i'm pretty sure there is some kind of collision when the pthreads are reading from the file at the same time) but at least you will have something to continue working with. </p> <p>I got this output:</p> <p>A</p> <p>T</p> <p>A</p> <p>T</p> <p>something </p> <p>something </p> <p>something </p> <p>something </p> <p>Process Number 4, Character = A</p> <p>Process Number 3, Character = A</p> <p>Process Number 2, Character = T</p> <p>Process Number 1, Character = T</p> <p>tail: no process found</p>
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    1. POreading characters line by line from a text file in c with multiprocessing
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    1. COit doesnt work for me, actually it stucks in a dead loop cause condition never be '1' actually. and i guess there is a wrong situation cause `child_pid` returns `0` when it is in child process and the parent should `default :` _? when i change it to default and set the child's condition to 0 it works but not properly. it prints wrong characters.
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    2. COyeah thats what i mean!. it prints wrong series of characters.
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    3. COas i said, its because the forked processes are all independent and there is nothing that controls the point in time when they print out the character they read. for example: p1 reads A, p2 reads B, p3 reads C, p2 prints B, p1 prints A, p3 prints C -> file is "A B C" but output is "B A C"
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