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Full Discussion: Explain iconv command
Top Forums UNIX for Beginners Questions & Answers Explain iconv command Post 303032462 by Corona688 on Monday 18th of March 2019 06:32:22 PM
Old 03-18-2019
dd can pad newline-terminated records to appropriate lengths with spaces, but they must be newline-terminated. Here is a utility to convert to newline-terminated records:

Code:
// convert to an executable with cc block.c -o block
#include <stdio.h>
#include <limits.h>
#include <stdlib.h>

int main(int argc, char *argv[]) {
        long int BLOCK=0;
        char *buf=NULL;

        if(argc < 2)
        {
                fprintf(stderr, "usage:  %s blocksize [inputfile]\n", argv[0]);
                exit(1);
        }

        if(argc >= 2) BLOCK=strtol(argv[1], NULL, 10);
        if(argc >= 3) {
                if(freopen(argv[2], "rb", stdin)==NULL)
                {
                        perror("Couldn't open");
                        return(1);
                }
        }

        if(BLOCK<=0)
        {
                fprintf(stderr, "Invalid block size %ld\n", BLOCK);
                return(1);
        }

        buf=malloc(BLOCK+1);
        if(buf == NULL)
        {
                perror("Couldn't allocate");
                return(1);
        }

//      fprintf(stderr, "block size %ld\n", BLOCK);

        buf[BLOCK]='\n';
        while(fread(buf,BLOCK,1,stdin))
                fwrite(buf,BLOCK+1,1,stdout);

        free(buf);
        return(0);
}

Having done that, you can convert it with iconv, pad to the required length with dd, then remove the newlines with tr.

In my example, I delete capital letters from aAabBbcccdDdeeEfffggghhhiIijjjkkklLlmmmnnn without changing length.

Code:
#!/bin/sh

BLOCKSIZE=3

# Add newlines using block utility
./block $BLOCKSIZE |
        # Remove characters, i.e. you'd put iconv here
        tr -d 'A-Z' |
        # Pad shrunken records with spaces
        dd ibs=$BLOCKSIZE cbs=$BLOCKSIZE conv=sync,block 2>/dev/null |
        # Remove newlines
        tr -d '\n'

Code:
$ cat fixed.txt
aAabBbcccdDdeeEfffggghhhiIijjjkkklLlmmmnnn

$ ./dump.sh < fixed.txt
aa bb cccdd ee fffggghhhii jjjkkkll mmmnnn   

$

You end up with one blank record at the end, full of spaces, which I haven't figured out how to avoid yet.
 

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LEARN ABOUT SUSE

tcl_concat

Tcl_Concat(3)						      Tcl Library Procedures						     Tcl_Concat(3)

__________________________________________________________________________________________________________________________________________________

NAME

       Tcl_Concat - concatenate a collection of strings

SYNOPSIS

       #include <tcl.h>

       const char *
       Tcl_Concat(argc, argv)

ARGUMENTS

       int argc (in)			      Number of strings.

       const char *const argv[] (in)	      Array of strings to concatenate.	Must have argc entries.
_________________________________________________________________

DESCRIPTION

       Tcl_Concat is a utility procedure used by several of the Tcl commands.  Given a collection of strings, it concatenates them together into a
       single string, with the original strings separated by spaces.  This procedure behaves differently than Tcl_Merge, in that the arguments are
       simply  concatenated:  no  effort  is made to ensure proper list structure.  However, in most common usage the arguments will all be proper
       lists themselves;  if this is true, then the result will also have proper list structure.

       Tcl_Concat eliminates leading and trailing white space as it copies strings from argv to the result.  If an element  of	argv  consists	of
       nothing but white space, then that string is ignored entirely.  This white-space removal was added to make the output of the concat command
       cleaner-looking.

       The result string is dynamically allocated using Tcl_Alloc;  the caller must eventually release the space by calling Tcl_Free.

SEE ALSO

       Tcl_ConcatObj

KEYWORDS

       concatenate, strings

Tcl									7.5							     Tcl_Concat(3)
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