Information not remembered when dealing with multiple lines in a file - c

Question

So let's say that a file has multiply lines each containing one word. I want to store the characters of every word in every line in a array. The code below clearly doesn't work because the -i is zeroed in every loop and the program starts storing characters in the 1st position of the array again. The code is:
while(1)
{
if(fgets(str, 50, fp) == NULL)
break;
for(i=0; i<strlen(str); i++)
p[i] = str[i];
}

Answer 1

you have separate counter variable for p and keep incrementing it to avoid
overwritting, like below.
int write_position = 0;
while(1)
{
if(fgets(str, 50, fp) == NULL)
break;
for(i=0; i<strlen(str); i++)
p[write_position++] = str[i]; // you will not lose previous ones here
}
at the end lenght of the array p is equal to write_position

Answer 2

Fix your file reading loop like this;
while (fgets(str, sizeof(yourString), fp) != NULL)
{
yourString[strlen(yourString) - 1] = '\0'; // delete the new line
printf("%s\n", yourString);
}
So simply in the above code, your while loop will be working until there is no another line to read in the file. In each turn of while loop, it will take one line from your file, and add it to your yourString char array. Notice that, fgets() will be taking newline characters too (\n) for every line in the file, so that we need to remove this characters from the array before we add another line in it.
Before the while loop, You need to declare a char array to store each line in it such as;
char yourString[stringSize];
You need to determine a stringSize for your array to make it has enough storage for your file.

Answer 3

the following proposed code snippet
performs the desired functionality
assumes that the array 'p[]' is an array of char pointers to pointers and contains (at least) enough entries to hold all the lines in the input file
no line in the input file is longer than 48 characters + newline
And now the proposed code:
#define MAX_LINE_LEN 50
char **p;
p = calloc( NUM_LINES_IN_FILE, sizeof( char * ) );
if( !p )
{
perror( "calloc failed" );
exit( EXIT_FAILURE );
}
// implied else, calloc successful
FILE *fp;
if( !(fp = fopen ( "inputFileName", "r" )) )
{
perror( "fopen failed" );
exit( EXIT_FAILURE );
}
// implied else, fopen successful
char str[ MAX_LINE_LEN ];
for( int i=0; fgets(str, sizeof( str ), fp); i++ )
{
// remove trailing newline char
str[ strcspn( str, '\n' ) ] = '\0';
p[i] = strdup( str );
}
fclose( fp );