Shell Programming and Scripting

time { F(){ set -- ${2:3} ${2:0:3} ; echo "$2${1//?/*}" ;} ; mapfile -c 1 -C F <file1 ;}
aba*****
cdc*******
efe******
a*b****

real	0m0.001s
user	0m0.003s
sys	0m0.000s

time awk '{x=substr($0,N+1); gsub(".","*",x); print substr($0,1,N) x}' N=3 file1 > /dev/null
real	0m0.038s
user	0m0.037s
sys	0m0.000s

time { while read ; do X="${REPLY:3}" ; echo "${REPLY:0:3}${X//?/*}" ;done <file1 >/dev/null ;}
real	0m0.177s
user	0m0.163s
sys	0m0.013s

time { F(){ set -- "${2:3}" "${2:0:3}" ; echo "$2${1//?/*}" ;} ; mapfile -c 1 -C F <file1 >/dev/null ;} 
real	0m0.286s
user	0m0.280s
sys	0m0.000s

time { while read line; do len=${#line} ; [ $len -gt 3 ] && len=$(( $len - 3)); tmp="$(printf '%*s' $len|sed s,\ ,*,g)"; echo "${line:0:3}${tmp}"; done<file1 >/dev/null;}
real	0m27.940s
user	0m12.867s
sys	0m1.340s

time perl -ne 'print substr($_,0,3)."*"x(length()-4)."\n"' file1 >/dev/null 
real	0m0.014s
user	0m0.010s
sys	0m0.000s

#include <stdio.h>
#include <string.h>
 
int main(){
    char buf[256];
    size_t sz ;
 
    while ( fgets( buf, sizeof buf, stdin )){
        if ( ( sz = strlen( buf )) < 5 ){
            fputs( buf, stdout );
        } else if ( sz == ( sizeof buf - 1 ) && buf[254] != '\n' ){
            fputs( "Line too long!\n", stderr );
            exit( 1 );
        } else {
            fwrite( buf, 3, 1, stdout );
            for ( sz -= 4 ; sz ; sz-- ){
                putchar( '*' );
            }
            putchar( '\n' );
        }
    }
 
    if ( ferror( stdin )){
        perror( "stdin" );
        exit( 2 );
    }
}

time ./a.out <file1 >/dev/null 

real	0m0.006s
user	0m0.003s
sys	0m0.000s

import java.io.BufferedReader; 
import java.io.InputStreamReader;  
 
public class star3 { 
 
    public static void main( String[] args ) {
 
        String buf ;

        BufferedReader stdin = new BufferedReader( new InputStreamReader( System.in ));
        int sz ; 
 
        try { 
           while (( buf = stdin.readLine()) != null ){

                if (( sz = buf.length()) < 4 ){
                    System.out.println( buf );
                } else {
                    System.out.print( buf.substring( 0, 3 )); 
 
                    for ( sz -= 3 ; sz > 0 ; sz-- ){
                         System.out.print( '*' );

                    } 
 
                    System.out.println(); 
                }

            }
        } catch( Exception e ){
            e.printStackTrace();
            System.exit( 1 ); 
        }
    }
}

time java star3 <file1 >/dev/null 

real	0m0.431s
user	0m0.527s
sys	0m0.073s