Rhino Skip Rack Pinion

C: read data from text files and discarding comments

Suppose you have a file like this

 # commento1 
 
 value 1 value # 2 
 commento2 
 value 3 
 # comment # comment 
 3 4 4 
 
 value value value 
 5 6 
 

Suppose you want to extrapolate from it the values \u200b\u200bexcluding the text is unnecessary for the comments.

The following describes a possbile way to do it.

 
 
 # include int main (void) {
 
 static const char filename [] = "file.txt"; 
 
 FILE * file = fopen (filename, "r"); 
 
 if (file! = NULL) {
 
 / * here, 4096 is the maximum line size * / 
 char line [4096]; 
 int i; 
 
 / * read a line * / 
 while (fgets (line, sizeof (line), file)! = NULL) {
 
 if (line [0 ]!='#') 
 
 {sscanf (line, "value % d \\ n ", & i); 
 printf ("% d \\ n ", i); 
} 
} 
 fclose (file); 
 
} 
 else 
 {
 perror (filename); 
} 
 
 return 0;} 
 
 

The execution of the program described in the input file shown above leads to the following implementation

 
 1 2 3 
 
 
 4 5 6 
 
 

The file is read line by line and comment lines are discarded (recognized by the character '#' first). If this is not the comment, the numeric value is extrapolated from the text string.

IMPORTANT: fgets not always read a line, it reads as many bytes as are specified by the second argument, in the presence of a symbol of "head" stop reading even though the number of bytes specified has not been achieved, and when this happens we can say that a row has been read, but for obvious reasons, you must be sure that the character length of a line does not exceed that specified as the second argument of fgets .

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