wrap.c

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

#define VERSION "0.3"
#define DATE "29 April 2024"

#define DEFAULT_WIDTH 80
#define MAX_LENGTH 32768
#define MIN_WIDTH     10

void help(void)
{
  printf(
	 "wrap " VERSION " - wrap text at n characters.\n"
	 "\n"
	 "wrap -e   # get width from $COLUMNS .\n"
	 "wrap -w n # set width to n .\n"
	 "wrap -h   # provide this help message.\n"
	 "\n"
	 "DEFAULT_WIDTH : %d.\n"
	 "MIN_WIDTH     : %d.\n"
	 "COLUMNS       : ",
	 DEFAULT_WIDTH, MIN_WIDTH);
  
  if (getenv("COLUMNS"))
    printf("%d.\n", atoi(getenv("COLUMNS")));
  else
    printf("(not set).\n");

  printf(
	 "\n"
	 "Michael Chappell\n"
	 DATE "\n"
	 "mcsuper5@freeshell.org\n"
	 "\n");
  return;
}

int main(int argc, char ** argv)
{
  int width=DEFAULT_WIDTH;
  int c;                   /* current character */
  int i=0;                 /* index into word */
  int length=0;            /* current line length */
  char word[MAX_LENGTH];

  if (argc>1) {
    /* While it is a bit of a hack, the option flag is usually
       "-" or "/" depending upon your operating system.  We will
       ignore the flag completely and generally ignore the
       length of the arguments.
    
       This may result in some weird uses: "wrap aeiou" is valid
       and is treated the same as "wrap -e".
    */
    switch (argv[1][1]) {
    case 'e':
      if (getenv("COLUMNS")) {
	width=atoi(getenv("COLUMNS"));
      } else {
	fprintf(stderr, "%s : getenv(\"COLUMNS\") failed, using default "
		"width.\n", argv[0]);
	fprintf(stderr, "\n"
		"Try adding \"export COLUMNS\" to your profile.\n");
	width=DEFAULT_WIDTH;
      }
      break;
    case 'w':
      if (argv[1][2] == '\0')
	width=atoi(argv[2]);
      else
	width=atoi(&argv[1][2]);
      break;
    default:
      help();
      return EXIT_SUCCESS;
      break;
    }
  }

  /* Is the width rational */
  if (width<MIN_WIDTH) {
    fprintf(stderr, "%s: Width %d is to small. Setting width to %d.\n",
	    argv[0], width, DEFAULT_WIDTH);
    width=DEFAULT_WIDTH;
  }
  
  while ((c=getchar())!=EOF) 
    {
      if ((c=='\n')&&(i==0)&&(length==0)) {
	printf("\n");
	continue;
      }
      if (isgraph(c)) {
	word[i++]=c;
      } else {
	word[i]='\0';

	if (c=='\n') {
	  if ((length+i)<width) {
	    printf("%s", word);
	    length=0;
	    i=0;
	  } else {
	    printf("\n%s ", word);
	    length=0;
	    i=0;
	  }
	  /* Emit the word and update length */
	} else if ((i+length)<width) {
	  printf("%s ", word);
	  length+=i+1;
	  i=0;
	} else {
	  /* Line would exceed width. wrap */
	  printf("\n%s", word);
	  if (c!='\n') {
	    printf(" ");
	    length=i+1;
	  } else {
	    printf("\n");
	    length=0;
	  }
	  i=0;
	}
      }
      /* We should be able to prevent an overflow by not allowing
	 i to increase beyond MAX_LENGTH-1
      */
      if (i==MAX_LENGTH-1) {
	word[i]='\0';
	printf("%s\n", word);
	length=0;
	i=0;
      }
      if (c=='\n')
	printf("\n");
    }
  word[i]='\0';
  if (c!='\n') {
    if ((length+i)>width)
      printf("\n");
    
    printf("%s\n", word);
  }
  
  return EXIT_SUCCESS;
}
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Wednesday, 9 July 2025 Michael J. Chappell Contact me at: mcsuper5@freeshell.org
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