Concatenating words without spaces.

Hi All,

I have written a C program to solve this problem but I am eager to know whether the same output can be obtained using sed or awk?

This is the input:

star
ferry
computer
symbol
prime
time

This is the output:

starferry
ferrycomputer
computersymbol
symbolprime
primetime

This is my code written in C.

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

char *chomp ( char * );

int32_t main ( int32_t argc , char ** argv )
{
    FILE *input_file = NULL;
    input_file = fopen ( argv [ 1 ] ,"r" );
    if ( input_file == NULL )
    {
        fprintf ( stderr , "input file open error\n" );
    }

    FILE *output_file = NULL;
    output_file = fopen ( "concatenated_words.dat" , "w" );
    if ( output_file == NULL )
    {
        fprintf ( stderr , "file write error\n" );
    }

    unsigned long int status_flag = 0;

    char *word1 = NULL;
    word1 = ( char * ) malloc ( 20 * sizeof ( char ) );
    if ( word1 == NULL )
    {
        fprintf ( stderr , "malloc() memory allocation failure\n" );
    }

    char *word2 = NULL;
    word2 = ( char * ) malloc ( 20 * sizeof ( char ) );
    if ( word2 == NULL )
    {
        fprintf ( stderr , "malloc() memory allocation failure\n" );
    }

    while ( !feof ( input_file ) )
    {
        if ( status_flag == 0 )
        {
            fscanf ( input_file , "%s\n" , word1 );
        }
        memset ( word2 , 0 , strlen ( word2 ) );
        fscanf ( input_file , "%s\n" , word2 );

        word1 = chomp ( word1 );
        word2 = chomp ( word2 );

        fprintf ( output_file , "%s%s\n" , word1 , word2 );
        status_flag ++;
        memset ( word1 , 0 , strlen ( word1 ) );
        strcpy ( word1 , word2 );
    }

    free ( word1 );
    free ( word2 );
    fclose ( input_file );
    fclose ( output_file );
}
              
char *chomp ( char *word )
{
    int32_t word_length = 0;
    word_length = strlen ( word );
    if ( word [ word_length ] == '\n' )
    {
        word [ word_length ] = '\0';
    }
    return ( word );
}

I am using gcc on Linux.

With sed:

sed 'N;h;s/\n//;P;g;D' inputfile

Try:

awk 'p{print p $0}{p=$0}' infile

The following should mimic the intent of that C code (including printing out the only line if there is only a single line in the input).

sed '1n;$q;p' | paste -d\\0 - -

Regards,
Alister

See how sed and awk can be terse compared to c?

awk 'p{print p $0}{p=$0}' infile

please tell me what does "p" in the start refers to ?

Only print if variable p contains something, which is the case on every line except the first line...

yes you are right. Its unbelievable