Parsing a Text file using C++

Applications Programming
1

I was trying to parse the text file, which will looks like this

###XYZABC####
############
int = 4
char = 1
float = 1
.
.
############

like this my text file will contains lots of entries and I need to store these entries in the map eg. map.first = int and map.second = 4 same way I will keep on inserting other elements into this

Anybody can help me on this.

Thanks in advance!!!

2

Why C++ when this can be done using awk or perl...much simpler especially if this is a one off thing.

3 
#include <stdio.h>
#include <ctype.h>

int main(void)
{
        char buf[512];
        FILE *fp=fopen("file.txt", "r");
        if(fp == NULL)
        {
                 fprintf(stderr, "Couldn't open file.txt\n");
                 return(1);
        }

        while(fgets(buf, 512, fp))
        {
                char *str=buf;
                char name[512], val[512];
                // Ignore whitespace at the beginning
                while(isspace(*str)) str++;
                // Ignore blank lines, comments
                if(((*str) == '\0') || ((*str) == '#') continue;

                // %[^= ] means string with no spaces or = chars.
                // then scanf expects a literal " = ", spaces optional.
                // lastly, %[^ \n] is a string with no spaces or newlines.
                // It returns '2' when it has found both strings and the = between.
                if(sscanf(str, "%[^= ] = %[^ \n]", name, val) == 2) 
                {
                        printf("Found value line, %s = %s\n", name, val);
                }              
        }

        fclose(fp);
}
4

If you really want to learn how write parser in C++ efficiently, then spend time with boost::spirit . The learning curve is steep at the beginning, but then the ROI is great :smiley:

/Lew

5

Thanks for the reply.

I will try this!!!

7

"Boost" is overkill for something that's accomplished with 3 libc calls, 5 if you count fopen/fclose...