Reading a file from command line

This is a discussion on Reading a file from command line within the C Programming forums, part of the General Programming Boards category; Hi guys, I recently have an assignment which will read a file from command line. e.g. myprogram < input 1.) ...

  1. #1
    Registered User
    Join Date
    Oct 2005
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    5

    Reading a file from command line

    Hi guys,

    I recently have an assignment which will read a file from command line.

    e.g. myprogram < input

    1.) Would like to clarify that the way to read the inputs of the file would be to use fgets()? I have also tried using fscanf, and am not sure on which to go with. I have also searched through this forum and found sscanf, again, not sure on which one to use.

    2.) A second problem I have encountered is that I have no idea on how to "break" the input up into how I want them to be.

    The contents of the input file is a mixture of alphabets and numbers.

    My understanding of fgets() is that it would read the whole line as a string right? So, for example the line read is " c918 = a1203 ". Could you point me in the right direction as to how I would convert that string "c918 = a1203" to an integer -> 918, and hex -> a1203.

    Thanks guys, appreciate the help

  2. #2
    a_capitalist_story
    Join Date
    Dec 2007
    Posts
    2,652
    Most likely you will use a combination of fgets to read a line from stdin, then sscanf to get the data into the variables required.

    fgets reads the entire line as a string, yes. It also leaves the newline in the buffer, so you should remove it like so:

    Code:
    char buffer[1024]; // This needs to be large enough to fit the largest line you'll read
    if (fgets(buffer, sizeof(buffer), stdin) != NULL)
    {
        // Remove the newline
        buffer[strlen(buffer) - 1] = 0;
    }
    As I stated above, use sscanf to get formatted input into variables. Google for sscanf and read the docs well.

  3. #3
    Registered User
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    Oct 2005
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    5
    Thanks mate, appreciate your help!

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