CODEWITHSUNDEEP
cregex
user1758596
user1758596

Reputation: 276

Assign variables from a string using regular expressions

I'm coding in C and I have a string which consists of values such like this

e=3213213123

n=321312321321321

How do I use regular expressions in order to assign int e and int n these values from a string?

Upvotes: 1

Views: 115

Answers (3)

unwind
unwind

Reputation: 399949

There's no way to directly match the string to a variable name; variable names are strictly a compile-time concept that are not present at run-time.

You need to do the matching (against a run-time list or array of variable names, probably), parsing of the value to be assigned, and finally the assignment as separate steps.

There's little point in using regular expressions here, something way simpler such as:

char vname[32];
int  value;

if(sscanf("%30s=%d", vname, &value) == 2)
{
  if(strcmp(vname, "e") == 0)
    e = value;
  else if(strcmp(vname, "n") == 0)
    n = value;
  else
    fprintf(stderr, "**Unknown variable name '%s'\n", vname);
}

should do it. Note that the above simply hard-codes the "list" of variable names, which is not very scalable if you need to support a large (more than three) number of variables.

Upvotes: 0

Some programmer dude
Some programmer dude

Reputation: 409356

Skip over the "e=" part, and use strtoll. No regular expressions needed.

Upvotes: 1

Jeyaram
Jeyaram

Reputation: 9484

atoi() which converts the string to integer.

strtol() - convert a string to a long integer.

Read man pages of these functions and choose according to your need.

The atoi() function converts the initial portion of the string pointed to by nptr to int. The behavior is the same as

strtol(nptr, (char **) NULL, 10); except that atoi() does not detect errors.

Upvotes: 0

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