I have a text.txt file and I want to read it and print its content in the Output Window of IDA Pro (Free version).

I wrote an .idc script as follows:

#include <idc.idc>

static main() {
    auto fp;
    auto toPrint;

    fp = fopen("C:\Users\bob\text.txt", "r"); // fp is a file handle

    toPrint = fgetc(fp);

    Message("%s is the string\n", toPrint);


enter image description here

But it gives me an unknown character as shown above. I also tried using toPrint = readstr(fp), but it does not work. (same unknown character)

PS: I'm analysing a 32 bit PE file. I could not use IDAPython, as I'm using the x64 free version, so I have to resort to IDC. Any help appreciated.

1 Answer 1


The variant below works for me.

static main() {
    auto fp;
    auto toPrint;
    fp = fopen("C:\\Users\\[cenzored]\\desktop\\text.txt", "r"); // fp is a file handle
    do {
        toPrint = readstr(fp);
         if (toPrint != -1)Message(toPrint);
    } while (toPrint != -1);

Actually there are 3 differences between your code and working variant:

  • it uses readstr which returns string
  • It avoids using format string in Message function (but Message("%s", toPrint) works too)
  • As in normal C I use double slash (\\ instead of \) for the path of the file. This is probably an initial cause of your problem: symbols preceded by single slash are interpreted as escape sequences which means that the file name was interpreted incorrectly and was not opened.

Using fgetc in a way you did is also incorrect because it returns long or character, not a string, and Message function probably interprets is as a pointer. I checked this on IDA 6.9. In a later versions it is probably better to detect an EOF by value_is_string function for this.

  • @w s Thank you for the help; I realised my mistake. Say, can you convert a string into an integer in IDC? eg. from '1510' to 1510?
    – Kyoma
    Commented May 24, 2018 at 15:31
  • @w s Nvm, got it. Use 'atol' command.
    – Kyoma
    Commented May 24, 2018 at 15:42

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