Reading a formatted input using scanf - c

Question

I want read from stdin some variables with their values using scanf.The input is formatted as below:
MY_VARIABLE_BEGIN
var1
var2
...
MY_VARIABLE_END
MY_VALUES_BEGIN
val1
val2
...
MY_VALUES_END
The input is composed of 2 parts:
part 1:Name of the variables this part is delimited by MY_VARIABLE_BEGIN ,MY_VARIABLE_END
part 2:The values of each variable this part is delimited by MY_VALUES_BEGIN, MY_VALUES_BEGIN
The problem is that i don't know the number of the variables and their values.
Can any body help me find the right format to pass to scanf function,or if there is any other solution to solve the problem?
Example of input
MY_VARIABLE_BEGIN
var1
var2
MY_VARIABLE_END
MY_VALUES_BEGIN
1
5
MY_VALUES_END
I should read 2 variables var1 and var2, var1=1 and var2=5

Answer 1

You can try this
char line[256];
fgets(line, sizeof(line), stdin);
if (strcmp(line, "MY_VARIABLE_BEGIN") {
do {
fgets(line, sizeof(line), stdin);
// . . . do something with the line
} while (strcmp(line, "MY_VARIABLE_END"));
}
Not sure if it'll work.

Answer 2

Doing it with scanf is a pain. Why not use a regular expression from C?
Here's a complete working program to show how easy it can be.
Start by reading all the data into a single string, data. I'm just using a constant.
Compile your pattern with regcomp, then apply it with regexec to your string.
It returns an array of matched groups which correspond to the (.*?) parts of the pattern.
Group 0 is of no interest in this example as it is just the entire data.
For the other 2 groups, you get the indexes in the string of the start and end of the match.
Use strndup() to copy these. Use strtok to split this dup on the newline \n character.
You have in ptr at each point each var and value.
/* regex example. meuh on stackoverflow */
#include <stdlib.h>
#include <sys/types.h>
#include <regex.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
void pexit(char *str){
extern int errno;
perror(str);
exit(errno);
}
#define NUMMATCH (1+2) /* max num matching capture groups in pattern */
main(int argc, char **argv){
regex_t myexpn;
regmatch_t matches[NUMMATCH] = {0};
int rc,i;
char *data = "\n\
MY_VARIABLE_BEGIN\n\
var1 \n\
var2\n\
...\n\
MY_VARIABLE_END\n\
MY_VALUES_BEGIN\n\
val1\n\
val2\n\
...\n\
MY_VALUES_END\n\
";
char *delim = "\n";
char *pattern = "\\s*MY_VARIABLE_BEGIN\\s*(.*?)MY_VARIABLE_END.*?MY_VALUES_BEGIN\\s*(.*?)MY_VALUES_END";
/* need REG_EXTENDED to use () in pattern else \\(\\) */
rc = regcomp(&myexpn, pattern, REG_EXTENDED);
if(rc!=0)pexit("regcomp");
rc = regexec(&myexpn, data, NUMMATCH, matches, 0);
if(rc==REG_NOMATCH)printf("no match\n");
else{
for(i = 1;i<NUMMATCH;i++){ /* ignore group 0 which is whole match */
if(matches[i].rm_so!=-1){
char *dup = strndup(data+matches[i].rm_so, matches[i].rm_eo-matches[i].rm_so);
printf(" match %d %d..%d \"%s\"\n",i, matches[i].rm_so, matches[i].rm_eo, dup);
char *ptr = strtok(dup, delim);
while(ptr){
printf(" token: %s\n",ptr);
ptr = strtok(NULL, delim);
}
free(dup);
}
}
}
regfree(&myexpn);
}
This prints out:
match 1 19..34 "var1
var2
...
"
token: var1
token: var2
token: ...
match 2 66..80 "val1
val2
...
"
token: val1
token: val2
token: ...