Carriage Returns

Discussion in 'C Programming' started by Nimmy, Oct 9, 2003.

  1. Nimmy

    Nimmy Guest


    I have a data file and I want to remove Carriage returns. Any one has any C
    code/program which does this? I am working on Windows XP machine.....I don't
    have access to UNIX machine. But I need to send this data file to the Unix
    machine once I remove the carriage retunrns from my XP machine.

    Nimmy, Oct 9, 2003
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  2. Here's a simple filter-type program.

    #include <stdio.h>
    int main(void) {
    int cr = '\r'; /* the code for carriage return */
    int c;
    while ((c = getchar()) != EOF) {
    if (c != cr) {
    return 0;

    Simply redirect stdin from the file you want to remove carriage
    returns from and redirect stdout to the new file.

    /-- Joona Palaste () ---------------------------\
    | Kingpriest of "The Flying Lemon Tree" G++ FR FW+ M- #108 D+ ADA N+++|
    | W++ B OP+ |
    \----------------------------------------- Finland rules! ------------/
    "You will be given the plague."
    - Montgomery Burns
    Joona I Palaste, Oct 9, 2003
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  3. No, both stdin and stdout are text streams by default. A one-to-one
    correspondence between the characters of a text stream and the
    external representation is not mandated by the standard. You need to
    use binary streams.
    =?ISO-8859-1?Q?Johan_Aur=E9r?=, Oct 9, 2003
  4. Nimmy

    Dan Pop Guest

    Had you engaged your brain, you'd have realised that your filter is
    useless for its intended purpose: stdin being a text stream, it won't
    see any CR character that is part of a CR+LF pair: such pairs are simply
    mapped to a '\n' character, when read from a text stream on a Windows
    platform. Furthermore, when you output a '\n' character, the C runtime
    system will turn it into a CR+LF pair.

    Of course, your program would work on a Unix system, but the OP wants
    to perform the conversion on the Windows side. The solution is
    incredibly simple, assuming that argv[1] contains the input file name and
    argv[2] the output file name. All error checking deliberately omitted:

    int c;
    FILE *in = fopen(argv[1], "r"), *out = fopen(argv[2], "wb");

    while ((c = getc(in)) != EOF) putc(c, out);

    Any CR that is part of a CR+LF pair will be automatically removed by the
    C runtime system, because the input file is opened in text mode. The
    opposite operation is not going to happen, because the output file is
    opened in binary mode.

    And you probably don't want to filter any CR that is not part of a CR+LF

    As a last remark, if the file is sent using the FTP protocol, the
    conversion will be automatically performed, if the transfer is made in
    text mode.

    Dan Pop, Oct 9, 2003
  5. Whoops. Serves me right for only ever testing this program on UNIX,
    which makes no distinction between text and binary streams. Thanks for
    the correction.

    /-- Joona Palaste () ---------------------------\
    | Kingpriest of "The Flying Lemon Tree" G++ FR FW+ M- #108 D+ ADA N+++|
    | W++ B OP+ |
    \----------------------------------------- Finland rules! ------------/
    "B-but Angus! You're a dragon!"
    - Mickey Mouse
    Joona I Palaste, Oct 9, 2003
  6. Greetings.

    How are you sending it to the Unix machine? Many FTP and other file
    transfer programs include options which automatically convert text files
    between DOS/Unix/Mac formats. A sufficiently powerful programmer's editor
    (e.g., (X)Emacs, UltraEdit) should also do this for you automatically. No
    need to reinvent the wheel.
    Tristan Miller, Oct 9, 2003
  7. Nimmy

    Default User Guest

    Tristan Miller wrote:

    There are also utilities that can do the transformation, dos2unix and

    Brian Rodenborn
    Default User, Oct 9, 2003
  8. ^^^^^^^^^^^ ^^^^^^^^^^^^^^^^^^^^^^^

    (snip source code)

    (snip Dan's quite well warranted criticism)
    Why? If we're being pedantic here, there was nothing in the OP's
    request that indicated we would be dealing with a text file.

    /-- Joona Palaste () ---------------------------\
    | Kingpriest of "The Flying Lemon Tree" G++ FR FW+ M- #108 D+ ADA N+++|
    | W++ B OP+ |
    \----------------------------------------- Finland rules! ------------/
    "I will never display my bum in public again."
    - Homer Simpson
    Joona I Palaste, Oct 9, 2003
  9. So just use "freopen()" to change "stdin" and "stdout"
    to binary mode. Then you can continue to use "getchar()"
    and "putchar()"...
    Charles Richmond, Oct 9, 2003
  10. Or BBEdit on the Macintosh...
    Charles Richmond, Oct 9, 2003
  11. And if they don't they need a jolly good slapping.
    Even Windows Wordpad can do this.
    Mark McIntyre, Oct 9, 2003
  12. Nimmy

    Dan Pop Guest

    Think harder...

    freopen() has the nasty habit of first closing the old stream (which a
    filter program cannot afford to do) and, in its pre-C99 incarnations,
    of requiring a valid file name.

    Dan Pop, Oct 10, 2003
  13. Nimmy

    Dan Pop Guest

    The mere words "carriage return" indicate a text file. '\r' becomes
    devoid of any special meaning when output to a binary stream.

    Dan Pop, Oct 10, 2003
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