Mixing BASH with C

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  1. #1
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    Mixing BASH with C

    How do you mix BASH with C. What I am trying to do is with a c-program take input into two arrays and then send them into any BASH command and execute the command. I have tried doing it with copy but with no luck.

    Code:
    #include <stdio.h>
    #include <stdlib.h>
    
    int main(void)
    {
    	char name1[20];
    	char name2[20];
    
    	printf("Please enter two names.\n");
    	scanf("%s %s", name1, name2);
    	
    	system("cp name1 name2");
    
    	return 0;
    }

  2. #2
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    Well I'm no Linux expert, but that system() call? name1 and name2 are parts of a string literal in that parameter. You're not referring to the arrays in that case. Rethink that, and then try again.

  3. #3
    Me -=SoKrA=-'s Avatar
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    use the exec function family. 'man 3 exec' should do it.
    SoKrA-BTS "Judge not the program I made, but the one I've yet to code"
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  4. #4
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    Do you want to have the two names passed as arguments to the executable, or do you want them to be sent via standard input? You are passing them as arguments, but keep in mind that many unix tools expect the data to arrive via standard input through a pipe redirection...
    The crows maintain that a single crow could destroy the heavens. Doubtless this is so. But it proves nothing against the heavens, for the heavens signify simply: the impossibility of crows.

  5. #5
    Frequently Quite Prolix dwks's Avatar
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    The program being executed is cp. cp expects arguments.

    sean_mackrory has a point. Use a temporary string for the call to system/exec.
    dwk

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    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
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  6. #6
    Just kidding.... fnoyan's Avatar
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    Hi

    system("cp name1 name2");

    You pass "cp name1 name2" to system() command! So, the command means
    "copy name1 as name1",it does not mean "copy the file whose name was defined by the user and contained in name1 as name2"!

    You have to declare a new char[] and then append it so that you construct a new array of char containing your bash commad. Maybe you want to have a look to sprintf()

    And one more suggestion, use fork()-exec() (actually one of exec family funcions) for calling another program inside of yours!

  7. #7
    Frequently Quite Prolix dwks's Avatar
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    Everything you posted can already be found in this thread. Except
    And one more suggestion, use fork()-exec() (actually one of exec family funcions) for calling another program inside of yours!
    See the FAQ on that topic: http://faq.cprogramming.com/cgi-bin/...&id=1043284392
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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