CODEWITHSUNDEEP
c++c
philleonard
philleonard

Reputation: 45

fprintf not writing "%" to file

So I'm trying to write this line to a text file;

sprintf(line, "%d, %f, %f, %f, %f, %f, %f, %f, %f, %f, %d, %s\n", 
          gen_no, total_time, 
          progp->total_fitness, 
          progp->entopy_breakdown[0], 
          progp->entopy_breakdown[1], 
          progp->entopy_breakdown[2], 
          progp->entopy_breakdown[3], 
          progp->entopy_breakdown[4], 
          progp->entopy_breakdown[5], 
          progp->entopy_breakdown[6], 
          0, 
          tree_as_char);

fprintf(fp, line);
fclose(fp);

Everything in the line is written correctly apart from when tree_as_char has "%" i.e. "%25" symbols in it (sometimes it writes one and then the proceeding char is escaped, sometimes it does't write any). All the other symbols in tree_as_char are written to the file correctly, and printing the line prints the % symbols correctly. Maybe I'm not escaping it properly somewhere?

Thanks!

Phil

Upvotes: 0

Views: 454

Answers (2)

Elias Van Ootegem
Elias Van Ootegem

Reputation: 76413

Oh dear, just noticed you're writing sprintf, and then call fprintf. Now that's just not necessary. You can easily save on that sprintf call by writing:

fprintf(fp, "%d, %f, %f, %f, %f, %f, %f, %f, %f, %f, %d, %s\n",
          gen_no, total_time, 
          progp->total_fitness, 
          progp->entopy_breakdown[0], 
          progp->entopy_breakdown[1], 
          progp->entopy_breakdown[2], 
          progp->entopy_breakdown[3], 
          progp->entopy_breakdown[4], 
          progp->entopy_breakdown[5], 
          progp->entopy_breakdown[6], 
          0, 
          tree_as_char);

That ought to work, and you won't have any more issues with the percent signs in the tree_as_char string. If you still need that line var for other things, you can choose: parse the line, adding secondary % chars before writing to the file pointer, use fwrite, or, better (perhaps): use fputs:

sprintf(line, "%d, %f, %f, %f, %f, %f, %f, %f, %f, %f, %d, %s\n",
          gen_no, total_time, 
          progp->total_fitness, 
          progp->entopy_breakdown[0], 
          progp->entopy_breakdown[1], 
          progp->entopy_breakdown[2], 
          progp->entopy_breakdown[3], 
          progp->entopy_breakdown[4], 
          progp->entopy_breakdown[5], 
          progp->entopy_breakdown[6], 
          0, 
          tree_as_char);
fputs(fp, line);

If you want to print a percent sign (%) using any of the *printf functions, you have to escape the percent sign itself. Just write %% to get one %:

printf("%d%%", 10);

will print 10%
If your tree_as_char contains percent signs, fprintf will just consider that as a placeholder, so you'll have to parse that string first, and add a second percent sign if needed.

Upvotes: 3

Sergej Christoforov
Sergej Christoforov

Reputation: 1614

fprintf will treat any % symbol in second parameter as a formatter. Try fprintf(fp, "%s", line);.

Upvotes: 4

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