reading in strings - problem with "\n"

[Richard Allbert]

Hi,

Yet another question!

I've been playing with my own tournament manager program.

When reading in the player names from a .ini file, using fgets()

Code: Select all

while(fgets(readinput , 512 , ini_file))
    {
etc...

I read in a list of player names from the text .ini file - these are then stored in an array player[64].

Each name is read in with a "\n" on the end.

So, when I come to write

"Player 1 vs Player 2"

to a file, it reads

"Player 1
vs Player 2"

How do I remove the "\n" from the end of the 'Player 1\n' ?

I have tried

Code: Select all

char game[256]

strcpy(game,player[0]);
strcat(game," v ");
strcat(game,player[1]);

But that doesn't work.

I've been hunting cplusplus.com for a while now, and no answer. It seems a simple problem?

Thanks!

Richard

[mathmoi]

Something like that should do it :

Code: Select all

char sz[50];

/* put somthing in sz */

/* This replace the last character of the string (in your case a '\n') by '\0' that is used to delimit the end of the string */
sz[len(sz) - 1] = '\0';

[Zach Wegner]

That won't work if the last line ends in EOF. Try:

Code: Select all

char *c;
if (c = strchr(readinput, '\n'))
    *c = '\0';

Anyways, I got rid of fgets a while ago, as I don't like artificial input limits. This came after I implemented UCI, which can potentially have very long input lines. Here's a generic function that will allocate a string big enough. No need to free() it either, as the buffer is free()d next time the function is called.

Code: Select all

char *getln(FILE *stream)
{
    int c;
    int size;
    static char *buffer = NULL;

    if (buffer != NULL)
    {
        free(buffer);
        buffer = NULL;
    }
    size = 0;
    while ((c = fgetc(stream)) != EOF)
    {
        if (buffer == NULL)
            buffer = malloc(1);
        else
            buffer = realloc(buffer, size + 1);
        buffer[size] = c;
        size++;
        if (c == '\0' || c == '\n')
            break;
    }
    return buffer;
}

[mathmoi]

I might add that if you are using C++ you should use std::string instead of C-style strings and ifstream instead of stdio.h.

[Richard Allbert]

I know... I just find some c functions easier.

[Richard Allbert]

Ok ,

Thanks for the reply, appreciated! I'll have a look.

Richard

[Richard Allbert]

Thanks again to you both..... it's worked.

[bob]

Hi,

Yet another question!

I've been playing with my own tournament manager program.

When reading in the player names from a .ini file, using fgets()

Code: Select all

while(fgets(readinput , 512 , ini_file))
    {
etc...

I read in a list of player names from the text .ini file - these are then stored in an array player[64].

Each name is read in with a "\n" on the end.

So, when I come to write

"Player 1 vs Player 2"

to a file, it reads

"Player 1
vs Player 2"

How do I remove the "\n" from the end of the 'Player 1\n' ?

I have tried

Code: Select all

char game[256]

strcpy(game,player[0]);
strcat(game," v ");
strcat(game,player[1]);

But that doesn't work.

I've been hunting cplusplus.com for a while now, and no answer. It seems a simple problem?

Thanks!

Richard

Simple solution:

char buffer[];
fgets(buffer, 128, in);
if (strchr(buffer, '\n'))
*strchr(buffer, '\n') = 0;

that will replace the \n on the end of a line with a null, which just shortens the string by one character.

[WinPooh]

Standard C++ allows more elegant solution:

Code: Select all

std::string s;
getline(std::cin, s);

No fixed limits in size, no '\n' problem.

[xsadar]

That won't work if the last line ends in EOF. Try:

Code: Select all

char *c;
if (c = strchr(readinput, '\n'))
    *c = '\0';

Anyways, I got rid of fgets a while ago, as I don't like artificial input limits. This came after I implemented UCI, which can potentially have very long input lines. Here's a generic function that will allocate a string big enough. No need to free() it either, as the buffer is free()d next time the function is called.

Code: Select all

char *getln(FILE *stream)
{
    int c;
    int size;
    static char *buffer = NULL;

    if (buffer != NULL)
    {
        free(buffer);
        buffer = NULL;
    }
    size = 0;
    while ((c = fgetc(stream)) != EOF)
    {
        if (buffer == NULL)
            buffer = malloc(1);
        else
            buffer = realloc(buffer, size + 1);
        buffer[size] = c;
        size++;
        if (c == '\0' || c == '\n')
            break;
    }
    return buffer;
}

That's a lot of calls to realloc. Why not something more like this?

Code: Select all

char *getln(FILE *stream)
{
    int c;
    int length = 0;
    static int size = 0;  // no need to allocate a new buffer every call
    static char *buffer = NULL;

    if (buffer == NULL)
    {
        // start with a buffer size you think is reasonable for your type of input
        buffer = malloc(32);
        size = 32;
    }
    while ((c = fgetc(stream)) != EOF)
    {
        if (length == size)
        {
            // double the size each time we reallocate
            buffer = realloc(buffer, size * 2);
            size *= 2;
        }
        buffer[length] = c;
        length++;
        if (c == '\0' || c == '\n')
            break;
    }
    return buffer;
}

Keep in mind I didn't test, or even compile it.