commands/simple/unexpand.c

   1 /*  unexpand - convert spaces to tabs   Author: Terrence W. Holm */
   2
   3 /*  Usage:  unexpand  [ -a ]  [ file ... ]  */
   4
   5 #include <stdlib.h>
   6 #include <string.h>
   7 #include <stdio.h>
   8
   9 #define  TAB   8
  10
  11
  12 int column = 0;                 /* Current column, retained between files  */
  13 int spaces = 0;                 /* Spaces since last tab stop       */
  14 int leading_blank = 1;          /* Only unexpand leading blanks,            */
  15 /* Overruled by -a option                   */
  16
  17 _PROTOTYPE(int main, (int argc, char **argv));
  18 _PROTOTYPE(void Unexpand, (FILE *f, int all));
  19
  20 int main(argc, argv)
  21 int argc;
  22 char *argv[];
  23
  24 {
  25   int all = 0;                  /* -a flag means unexpand all spaces  */
  26   int i;
  27   FILE *f;
  28
  29   if (argc > 1 && argv[1][0] == '-') {
  30         if (strcmp(argv[1], "-a") == 0)
  31                 all = 1;
  32         else {
  33                 fprintf(stderr, "Usage:  unexpand  [ -a ]  [ file ... ]\n");
  34                 exit(1);
  35         }
  36
  37         --argc;
  38         ++argv;
  39   }
  40   if (argc == 1)
  41         Unexpand(stdin, all);
  42   else
  43         for (i = 1; i < argc; ++i) {
  44                 if ((f = fopen(argv[i], "r")) == NULL) {
  45                         perror(argv[i]);
  46                         exit(1);
  47                 }
  48                 Unexpand(f, all);
  49                 fclose(f);
  50         }
  51
  52
  53   /* If there are pending spaces print them.  */
  54
  55   while (spaces > 0) {
  56         putchar(' ');
  57         --spaces;
  58   }
  59
  60   return(0);
  61 }
  62
  63 void Unexpand(f, all)
  64 FILE *f;
  65 int all;
  66
  67 {
  68   int c;
  69
  70   while ((c = getc(f)) != EOF) {
  71         if (c == ' ' && (all || leading_blank)) {
  72                 ++column;
  73                 ++spaces;
  74
  75                 /* If we have white space up to a tab stop, then output  */
  76                 /* A tab. If only one space is required, use a ' '.      */
  77
  78                 if (column % TAB == 0) {
  79                         if (spaces == 1)
  80                                 putchar(' ');
  81                         else
  82                                 putchar('\t');
  83
  84                         spaces = 0;
  85                 }
  86                 continue;
  87         }
  88
  89         /* If a tab character is encountered in the input then          */
  90         /* Simply echo it. Any accumulated spaces can only be           */
  91         /* Since the last tab stop, so ignore them.                     */
  92         if (c == '\t') {
  93                 column = (column / TAB + 1) * TAB;
  94                 spaces = 0;
  95                 putchar('\t');
  96                 continue;
  97         }
  98
  99         /* A non-space character is to be printed. If there   */
 100         /* Are pending spaces, then print them. There will be */
 101         /* At most TAB-1 spaces to print.                     */
 102         while (spaces > 0) {
 103                 putchar(' ');
 104                 --spaces;
 105         }
 106
 107         if (c == '\n' || c == '\r') {
 108                 column = 0;
 109                 leading_blank = 1;
 110                 putchar(c);
 111                 continue;
 112         }
 113         if (c == '\b')
 114                 column = column > 0 ? column - 1 : 0;
 115         else
 116                 ++column;
 117
 118         leading_blank = 0;
 119         putchar(c);
 120   }
 121 }