Exercise 3.2 - escape sequences into the real characters#
Question#
Write a function escape(s,t) that converts characters like newline and tab into visible escape sequences like n and t as it copies the string t to s. Use a switch. Write a function for the other direction as well, converting escape sequences into the real characters.
/* Write a function escape(s,t) that converts characters like newline and tab into visible escape sequences like \n and \t as it copies the string t to s. Use a Switch. Write a function for
the other direction as well,converting the escape sequences into the real characters */
#include<stdio.h>
#define MAXLINE 1000
int mgetline(char line[],int maxline);
void escape(char s[],char t[]);
int main(void)
{
char s[MAXLINE],t[MAXLINE];
mgetline(t,MAXLINE);
escape(s,t);
printf("%s",s);
return 0;
}
void escape(char s[],char t[])
{
int i,j;
i=j=0;
while(t[i] != '\0')
{
switch(t[i])
{
case '\t':
s[j]='\\';
++j;
s[j]='t';
break;
case '\n':
s[j]='\\';
++j;
s[j]='n';
break;
default:
s[j]=t[i];
break;
}
++i;
++j;
}
s[j]='\0';
}
int mgetline(char s[],int lim)
{
int i,c;
for(i=0;i<lim-1 && (c=getchar())!=EOF;++i)
s[i]=c;
s[i]='\0';
}
Explanation#
C Program interpreters \n and \t as space characters and outputs them. Our
intention is to capture the \n and \t characters and display them visibly as
n or t. In order to do that we need to escape them, the escaping is
done by adding \ character.
So in the program as soon as we see a \n character, in the array where we are
copying to, we copy \\ character and add a n character and similarly, when
we see a \t character, in the array where we are copying to, we copy \\
character and add a t character.