Locating and translating escape sequences to other values

Question

What would you use to check for escape sequenced values? I have two inputs arg1 and arg2. If you enter ab\t xyz into the arguments. And then if you were to type in "ab\t" into the input you would get "xyz" as output. I hope this makes sense and im really stuck at the escape character handling. Currently the code works for all except for when there are escape chars or if one argument is longer than the other.

it is a c code we wrote on our own the plan is to make a custom tr() function
void tr_str(char s[], char news[]){
    int c;
    size_t k =0;
        while ((c = getchar()) != EOF)
        {
            for(k=0; k < strlen(s);k++)
            {                   
                if(c == s[k])
                {
                    c = news[k];
                }
            }
            putchar(c);
        }
    }

it is a c code we wrote on our own the plan is to make a custom tr() function — TheUnknown, Feb 05 '15 at 22:30
how do you input \t? from the keyboard? piped in from a file? does c ever end up having \t in it? — pm100, Feb 05 '15 at 22:46
You use standard input with command line. The arguments are entered at ./a (arguments). I have a way to read everything in main but the problem is that currently it takes the '\' as a separate char from 't' for example. — TheUnknown, Feb 05 '15 at 22:47
After `c = news[k];` add `break;` to prevent any chance that `c` is translated back again further along the array. — Weather Vane, Feb 05 '15 at 23:23
[Escape all special characters in printf](http://stackoverflow.com/questions/22150946/escape-all-special-characters-in-printf) or [my answer](http://stackoverflow.com/questions/22150946/escape-all-special-characters-in-printf/22152332#22152332) may help — chux - Reinstate Monica, Feb 06 '15 at 00:01

Weather Vane · Answer 1 · 2015-02-06T00:12:56.317

EDIT:

I have interpreted escape chars in two ways. First the tab character is in the array s[], and secondly I trap the \ char in the escape sequence of \t and use a second pair of arrays to translate the escape sequence.

#include <stdio.h>
#include <string.h>

int main(void) { 
    char s[]="abcd\t";
    char news[]="ABCD!";
    char e[]="t";
    char newe[]="!";
    int c, k, esc = 0;
    while ((c = getchar()) != EOF) {
        if (esc) {
            for (k=strlen(e)-1; k>=0; k--) {
                if (c == e[k]) {
                    c = newe[k];
                    break;
                }
            }
            putchar(c);
            esc = 0;
        }
        else if (c == '\\') {
            esc = 1;
        } 
        else {
            for (k=strlen(s)-1; k>=0; k--) {
                if (c == s[k]) {
                    c = news[k];
                    break;
                }
            }
            putchar(c);
        }
    }
    return 0;
}

Program input (the spaces result from the tab key)

a\tz      d

Program output:

A!z!D

i suspect the OP problem is trying to enter the \t character into the args when running it from the command line- ie tr "abcd\t" "xyxpq", he seems to be saying that he ends up with \ and t — pm100, Feb 05 '15 at 23:43
@pm100 answer improved, a similar way can be used if the input comes from a program argument, but OP uses `getchar()`. — Weather Vane, Feb 06 '15 at 00:14

Locating and translating escape sequences to other values

1 Answers1