Read in text file with multiple elements per line - c

Question

I need to read in a text file, "input.in", so that I can run a sort function on the code, according to id. The input.in file contains an id and name of file, 8 lines total. I know that I need to read in the input file line by line (not sure if my code is correct). But the main problem is that the fopen function is returning the result that it can't find the input file, even though its on the desktop along with the source file being saved there.
Any tips would be greatly appreciated
int main()
{
int id;
char node;
char item[9], status;
FILE *fp;
if((fp = fopen("/Users/jacobsprague/Desktop/input.txt", "r+")) == NULL)
{
printf("No such file\n");
exit(1);
}
while(42)
{
int ret = fscanf(fp, "%s %c", id, &node);
if(ret == 2)
printf("\n%s \t %c", id, node);
else if(errno != 0)
{
perror("scanf:");
break;
}
else if(ret == EOF)
{
break;
}
else
{
printf("No match.\n");
}
}
printf("\n");
if(feof(fp))
{
puts("EOF");
}
return 0;
}
Here is the input file contents:
8
4 Node1111
8 Node11111111
2 Node11
7 Node1111111
1 Node1
5 Node11111
6 Node111111
3 Node111

Answer 1

fopen can fail for reasons other than not finding the file, so you should check errno to see what the problem was. However in this case, as BLUEPIXY has mentioned, the problem appears to be that you have typed input.txt instead of input.in.

Answer 2

// 1) there were lots of little oops in the ops code,
// 2) the op skipped the detail that the first line contains
// a count of the number of following lines
// all of that is corrected in the following
#include <stdio.h>
#include <stdlib.h>
int main()
{
int id; // value read from file
char node[30]; // string read from file
//char item[9]; // if not commented, raises compiler warning about unused variable
//char status; // if not commented, raises compiler warning about unused variable
int ret; // returned value from fscanf
int lineCount = 0; // number of lines in file after first line
int i; // loop counter
FILE *fp;
if((fp = fopen("/Users/jacobsprague/Desktop/input.in", "r")) == NULL)
{
// perror also outputs the value of errno and the results of strerror()
perror( "fopen failed for file: input.in");
exit(1);
}
// implied else, fopen successful
// get first line, which contains count of following lines
if( 1 != (ret = fscanf(fp, " %d", &lineCount)) )
{ // fscanf failed
perror( "fscanf"); // this also outputs the value of errno and the results of strerror()
exit( EXIT_FAILURE );
}
// implied else, fscanf successful for lineCount
for( i=0; i < lineCount; i++) // read the data lines
{
// note leading space in format string to consume white space (like newline)
if( 2 != (ret = fscanf(fp, " %d %s", &id, node)) )
{ // fscanf failed
// this also outputs the value of errno and the results of strerror()
perror( "fscanf for id and node failed");
break;
}
// implied else, fscanf successful for id and node
printf("\n%d\t %s", id, node);
} // end for
printf("\n");
if( EOF == ret )
{
puts("EOF");
} // endif
return 0;
} // end function: main