How can I find the number of terminal columns from a C/C++ program?

Question

Possible Duplicate:
Getting terminal width in C?

On Linux and OS X, my shell reports $COLUMNS has the width of the terminal window -- and resizing the window will adjust this shell variable.

But in my C/C++ program, getenv("COLUMNS") doesn't seem to find the variable.

Anybody have an explanation? Or an alternate suggestion for letting my C++ program figure out the width of the terminal it's running in (for some help message word wrapping)?

`$LINES` and `$COLUMNS` are *shell* variables, not *environment* variables. — Oliver Charlesworth, Jul 11 '11 at 21:55

score 11 · Accepted Answer · edited May 23 '17 at 12:25

11

Perhaps something like this:

#include <sys/ioctl.h>
#include <stdio.h>

int main()
{
    struct winsize w;
    ioctl(0, TIOCGWINSZ, &w);

    printf("lines %d\n", w.ws_row);
    printf("columns %d\n", w.ws_col);
    return 0;
}

Taken straight from: Getting terminal width in C?

edited May 23 '17 at 12:25

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answered Jul 11 '11 at 21:58

LainIwakura

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BTW this is not "portable" (not specified by POSIX) but works almost everywhere in practice. – R.. GitHub STOP HELPING ICE Jul 11 '11 at 22:18
Works great in my case, thanks! – Larry Gritz Jul 11 '11 at 22:38
3

You'll have to handle the `SIGWINCH` signal as well if you want to deal with resizing of the window. – Matthew Slattery Jul 11 '11 at 23:27

How can I find the number of terminal columns from a C/C++ program?

1 Answers1