1 files changed, 61 insertions, 6 deletions
diff --git a/userspace/grep.c b/userspace/grep.c
index 68d5b7a..058f1f8 100644
--- a/userspace/grep.c
+++ b/userspace/grep.c
@@ -1,18 +1,73 @@
 #include <stdio.h>
 #include <stdlib.h>
 
+// https://www.programmingsimplified.com/c/source-code/c-program-insert-substring-into-string
+//
+char *substring(char *string, int position, int length) 
+{
+   char *pointer;
+   int c;
+ 
+   pointer = malloc(length+1);
+ 
+   if( pointer == NULL )
+       exit(EXIT_FAILURE);
+ 
+   for( c = 0 ; c < length ; c++ ) 
+      *(pointer+c) = *((string+position-1)+c);       
+ 
+   *(pointer+c) = '\0';
+ 
+   return pointer;
+}
+
+
+void insert_substring(char *a, char *b, int position)
+{
+   char *f, *e;
+   int length;
+ 
+   length = strlen(a);
+ 
+   f = substring(a, 1, position - 1 );      
+   e = substring(a, position, length-position+1);
+ 
+   strcpy(a, "");
+   strcat(a, f);
+   free(f);
+   strcat(a, b);
+   strcat(a, e);
+   free(e);
+}
+
 int main(int argc, char **argv)
 {
+	char col_start[]="\033[31;40m";
+	char col_end[]="\033[37;40m";
+
 	FILE *in=stdin;
 	FILE *out=stdout;
 
-	while(1)
+	int i=1;
+	while(!feof(in))
 	{
-	    char buf[2];
-	    int l=fread(buf,1,1,in);
-	    if(l==0)break;
-	    buf[l]=0;
-	    fwrite(buf,1,l,out);
+	    char buf[256];
+	    char buf2[255];
+	    fgets(buf,255,in);
+
+	    char *pos=strstr(buf,argv[1]);
+	    if(pos)
+	    {
+		int p=pos-buf+1;
+		int l=strlen(argv[1])+strlen(col_start);
+
+		insert_substring(buf,col_start,p);
+		insert_substring(buf,col_end,p+l);
+
+		printf("%s",buf);
+	    }
+
+	    i++;
 	}
 
 	return EXIT_SUCCESS;