How to trim '\n' from the end of fgets() output

Question

I want to trim newline character from fgets output.

while(fgets(buff,1024,fp) ){

    printf("start%send",buff );

If there is a line "C is cool", in the file . Then the above code prints.

startC is cool
end

But I want it to print like

 startC is coolend

How to do that

@Lashane: That's dangerous in the case where there was no input (EOF) and `strlen(buff)` is 0. — R.. GitHub STOP HELPING ICE, Dec 31 '15 at 17:56

Weather Vane · Accepted Answer · 2015-12-31T18:14:15.050

7

Clean approach

#include <string.h>

//...

buff [ strcspn(buff, "\r\n") ] = 0;

This will work safely for any flavour of line endings, even if there is none present, and even if the string is empty.

edited Dec 31 '15 at 18:14

answered Dec 31 '15 at 17:36

Weather Vane

Nice approach but the comment is misleading and contrary to the rest of the answer. – R.. GitHub STOP HELPING ICE Dec 31 '15 at 17:57
@R.. thanks but can you please explain your remark about my comment? – Weather Vane Dec 31 '15 at 17:59
The comment says *trailing* newlines, but what your code actually does is truncate the string at the first newline (or carriage return) character. `fgets` cannot produce a newline except a trailing one, but there can be plenty of embedded carriage returns. – R.. GitHub STOP HELPING ICE Dec 31 '15 at 18:06
@R.. if there are, then you can modify the code to suit. But I don't usually encounter "plenty of embedded carriage returns" in a text file. Even if it's a code source file, in a string literal, they would be escaped. – Weather Vane Dec 31 '15 at 18:18
Indeed. I don't think it's a major practical concern, just that the comment is unsettling. I +1'd anyway. – R.. GitHub STOP HELPING ICE Dec 31 '15 at 18:19
@R.. I tweaked it slightly, thank you. – Weather Vane Dec 31 '15 at 18:20

score 2 · Answer 2 · edited Jan 01 '16 at 03:53

2

You can set the last character to '\0' (null terminator). This is not a good approach because the file may not have always have a newline.

buff[strlen(buff) - 1] = '\0';

or loop over the char array end replace the '\n' with '\0'

int i;
for(i = 0; i < strlen(buff); i++)
{
    if(buff[i] == '\n')
    {
        buff[i] = '\0';
        break;
    }
}

or remove the '\n' at the end with strcspn():

buff[strcspn(buff, "\r\n")] = 0;

edited Jan 01 '16 at 03:53

Jonathan Leffler

answered Dec 31 '15 at 17:41

John G

The last line read from a file might not have a `newline`, in which case your first example is weak. The `newline` is not added by `fgets`, it is what was in the file. – Weather Vane Dec 31 '15 at 17:45
True, I only included it because it is an approach that would work for this question. I'll edit to clarify that it's not a good approach. – John G Dec 31 '15 at 17:48
If `strlen(buff)` is 0 this produces dangerous undefined behavior. – R.. GitHub STOP HELPING ICE Dec 31 '15 at 17:57
that wouldn't happen in this case because fgets would return a null pointer which would cause the while loop condition to fail – John G Dec 31 '15 at 18:05

2 Answers2