Thread: Explain This Basic Program To Beginner

Hi,

I am working my way through a C Programming book but I am confused by this extract of code from book, which is suppose to locate lines ending with 'ould' and print them.

Code:

#include <stdio.h>												
   #define MAXLINE 1000 /* maximum input line length */					
   int getline(char line[], int max)   int strindex(char source[], char searchfor[]);					
   char pattern[] = "ould";   /* pattern to search for */					
   /* find all lines matching pattern */   main()					
   {       char line[MAXLINE];       int found = 0;					
       while (getline(line, MAXLINE) > 0)           if (strindex(line, pattern) >= 0) {					
               printf("%s", line);					found++;}
					
       return found;   }					
   /* getline:  get line into s, return length */   int getline(char s[], int lim)					{
int c, i;
					
       i = 0;       while (--lim > 0 && (c=getchar()) != EOF && c != '\n')					
           s[i++] = c;       if (c == '\n')				
			
							[IMG]file:///page63image24688[/IMG]			
							[IMG]file:///page63image24960[/IMG]			
							[IMG]file:///page63image25232[/IMG]			
												s[i++] = c;
				
			
		
														s[i] = '\0';
					return i;}
					
/* strindex:  return index of t in s, -1 if none */int strindex(char s[], char t[])					{
int i, j, k;
					
    for (i = 0; s[i] != '\0'; i++) {        for (j=i, k=0; t[k]!='\0' && s[j]==t[k]; j++, k++)					
            ;        if (k > 0 && t[k] == '\0')				
			
												}
				
									return i;
				
			
			
return -1;} 

What does the following:

Code:

#define MAXLINE 1000

actually mean, is 'MAXLINE' a built in function of C or something which they have created?

Then they use:

Code:

getline(char line [], int max)

So 'getline' is fairly self explanatory, then they indicate the type or result they are expecting which is 'char' for character. Now is that being put into a array, I am wondering because of '[]'? Furthermore, what is the 'int max' for?

Everything after that makes sense, they create a char array but why does it equal "ould", I know that the snipet that they are searching for.

Code:

char pattern[] = "ould";

Now we create another array called line, which refers to that 'MAXLINE' from earlier?

Code:

 main()						
   {       char line[MAXLINE];       int found = 0;			
       while (getline(line, MAXLINE) > 0)           if (strindex(line, pattern) >= 0) {			
               printf("%s", line);			found++;}
			
       return found; 
   }

Then we use a while loop, so while there is a line search for pattern and then print the string.

Grab any decent C language tutorial from the web and start reading.

Is there any you recommend, the one I got doesn't sem to be for begginers?

C Book Recommendations <-- lots of good stuff here

I got the first book, it doesn't seem great for beginner.

It's not great for a beginner. It's a dense, dry reference book, and quite out of date with the latest C standard (which itself is 12 years old). Try the "21 days" book, many here seem to like it as a total beginner's book.

Code:

#define MAXLINE 1000

During the preprocessing step (before the file is compiled) all instances of the word MAXLINE are replaced with 1000.

Originally Posted by ASHWHIT

Is there any you recommend, the one I got doesn't sem to be for begginers?

Go get a different one... Really...