strings

[smartset]

if (line[strlen(line)-1]=='\n')
{
line[strlen(line)-1]='\0';
}

If anyone expalin how this code works? why 1 is deducted ?

thanks

[Markus]

In C, array indexes start at 0. If strlen() returns 15 on an array that has was declared to have 14 elements, accessing array[strlen(array)] would evaluate to array[15]. Of course, as you can see this means we are going outside the bounds of the array (because the array index starts at 0). If we were to do array[strlen(array) - 1], we would then be accessing the last element of the array.

Mark.

P.S. Please see the posting guidelines on how to ask a question, specifically the part on using [code] tags.

[smartset]

Hello Mark,

Thanks for replly. But still confused as I'm not getting but will happen if we pass "Hello" as a strings and if we pass "Hello World" in an array of arr[10].

Thanks,

[smartset]

In the following program what is the purpose of defininig these two lines code?

if (line[strlen(line)-1]=='\n')
{
line[strlen(line)-1]='\0';
}


#include <stdio.h>
#include <string.h>
#include <stdlib.h>
int main(int numParms, char *parms[])
{
const int LINE_SIZE = 1000;
const int STRING_SIZE = 100;
const int NUM_STRINGS = 100;
FILE *infile;
char strings[NUM_STRINGS][STRING_SIZE];
char line[LINE_SIZE];
char* result;
int size;
int count;
size = 0;
infile = fopen("in.txt", "r");
result = fgets(line, LINE_SIZE, infile);
while (result != NULL)
{
if (line[strlen(line)-1]=='\n')
{
line[strlen(line)-1]='\0';
}
if ((size>=NUM_STRINGS) || (strlen(line)>=STRING_SIZE))
{
fprintf(stderr, "\nRan out of memory.\n");
exit(EXIT_FAILURE);
}
strcpy(strings[size], line);
printf("<%s>\n", line);
result = fgets(line, LINE_SIZE, infile);
size++;
}
fclose(infile);
printf("\n");
for (count=0; count<size; count++)
{
printf("<%s>\n", (char*) strings[count]);
}
printf("\nAll done\n");
return 0;
}

Thanks.

[Markus]

@smartset
Try it and see for yourself - experimentation is a good way to learn and understand things (though I should note this was not your original question).

[spiralfire]

@smartset
If you create a array of 10 elements, you will have 10 positions, but the first one is 0, so you will have an array from [0] to [9], thats 10 elements.

If you build a "Hello" string(lets say called st) it will be like this:

st[0] = 'H';
st[1] = 'e';
st[2] = 'l';
st[3] = 'l';
st[4] = 'o';
st[5] = '\0';
 

This array could have a minimum of 6 elements..
strlen would return 5, so the '\0' is st[strlen(st)], so i don't think that -1 should be there.. but i can be wrong..

the '/0' char represents the end of the string. '\n' means a change of line (enter button). So that code is reading lines of the file you specified, those end with a '\n', because you are using fgets, so that will return a line of the file, putting that string in a char array, and changing the '\n' to a end of string.

[smartset]

Thanks. Now I got a clear idea of this code.
:)