Selecting lines with length, C filter - c

Question

I am writing a filter that should select all lines having a specified length. I ended up having this code, but I don't know how to specify n. I mean, n (and optionally m) should be replaced by a number of lines in command prompt, but I have no idea how to describe it in the code. I thought of case "%d", but from what I know it's not possible to write it like that. That's the code I have so far:
#include<stdio.h>
#include<string.h>
int main(int argc, char *argv[])
{
int n;
int m;
char line[200];
while(fgets(line,sizeof(line)/sizeof(char), stdin)!=NULL)
{
if(argc>1){
switch(argv[0][0])
{
case 'n':
strlen(line)==n;
break;
case '#n':
strlen(line)<n;
break;
case 'n m':
strlen(line)>=n && strlen(line)<=m;
break;
case 'n#':
strlen(line) > n;
break;
}
printf("%s\n", line);
}}
return 0;
}
Your help would mean a lot to me! I don't really know how to make it work anymore.

Answer 1

I think you should parse the command line outside of your loop. Assuming you are going to require the caller of your program to specify both n and m on the command line, it's a simple matter of grabbing the first two parameters and converting them to integers, and then loop over your stdard input. Something like this:
/* call this minmax.c */
#include <stdlib.h>
#include <stdio.h>
int main(int argc, char* argv[]) {
int n, m, len;
char line[200];
if (argc < 3) {
printf("Must specify min & max line length.");
return -1;
}
n = atoi(argv[1]);
m = atoi(argv[2]);
while(fgets(line, 200, stdin) != NULL) {
len = strlen(line);
if (len >=n && len <= m)
printf(line);
}
return 0;
}
Assuming you are running on *nix:
cc -ominmax minmax.c
Then call it with the min and max line lengths
./minmax 2 5
This will echo back every line you type that is at least 2 characters, but no more then 5.

Answer 2

I hope I understand well the aim of your desired program and here is the code :
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main(int argc, char *argv[])
{
int i=1,n,m; // n and m are the variable which holds
// the limited length
if(argc>=3)
{
// you need to execute the program with this form
// program.exe n m <file.txt
n=atoi(argv[1]); // get the value of n
m=atoi(argv[2]); // get the value of m
printf("n=%d m=%d\n",n,m);
}
char line[1000]; // this variable will hold each line of the file
while (fgets(line,sizeof(line),stdin)) // fgets used to read
{ //the lines in file till the newline
int length=strlen(line)-1;
// we decrement the length to get rid of
// the newline character
if (length < n)
{
printf("line %d:%s status: < %d\n",i,line,n);
}
else if (length==n)
{
printf("line %d:%s status: = %d\n",i,line,n);
}
else if (length>n && length <=m)
{
printf("line %d:%s status: %d < <= %d\n",i,line,n,m);
}
else
{
printf("line %d:%s status: > %d\n",i,line,m);
}
i++;
}
return 0;
}
In case the code does not fit to your needs I think it is sufficient and can be taken as a support for your exact program as it encompasses everything you need !! Hope it helps !!