add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/unexpand.c

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+/*  unexpand - convert spaces to tabs	Author: Terrence W. Holm */
+
+/*  Usage:  unexpand  [ -a ]  [ file ... ]  */
+
+#include <stdio.h>
+
+#define  TAB   8
+
+
+int column = 0;			/* Current column, retained between files  */
+int spaces = 0;			/* Spaces since last tab stop  	    */
+int leading_blank = 1;		/* Only unexpand leading blanks,	    */
+/* Overruled by -a option	            */
+
+main(argc, argv)
+int argc;
+char *argv[];
+
+{
+  int all = 0;			/* -a flag means unexpand all spaces  */
+  int i;
+  FILE *f;
+
+  if (argc > 1 && argv[1][0] == '-') {
+	if (strcmp(argv[1], "-a") == 0)
+		all = 1;
+	else {
+		fprintf(stderr, "Usage:  unexpand  [ -a ]  [ file ... ]\n");
+		exit(1);
+	}
+
+	--argc;
+	++argv;
+  }
+  if (argc == 1)
+	Unexpand(stdin, all);
+  else
+	for (i = 1; i < argc; ++i) {
+		if ((f = fopen(argv[i], "r")) == NULL) {
+			perror(argv[i]);
+			exit(1);
+		}
+		Unexpand(f, all);
+		fclose(f);
+	}
+
+
+  /* If there are pending spaces print them.  */
+
+  while (spaces > 0) {
+	putchar(' ');
+	--spaces;
+  }
+
+  exit(0);
+}
+
+
+Unexpand(f, all)
+FILE *f;
+int all;
+
+{
+  int c;
+
+  while ((c = getc(f)) != EOF) {
+	if (c == ' ' && (all || leading_blank)) {
+		++column;
+		++spaces;
+
+		/* If we have white space up to a tab stop, then output	 */
+		/* A tab. If only one space is required, use a ' '.	 */
+
+		if (column % TAB == 0) {
+			if (spaces == 1)
+				putchar(' ');
+			else
+				putchar('\t');
+
+			spaces = 0;
+		}
+		continue;
+	}
+
+	/* If a tab character is encountered in the input then		*/
+	/* Simply echo it. Any accumulated spaces can only be 		*/
+	/* Since the last tab stop, so ignore them.			*/
+	if (c == '\t') {
+		column = (column / TAB + 1) * TAB;
+		spaces = 0;
+		putchar('\t');
+		continue;
+	}
+
+	/* A non-space character is to be printed. If there   */
+	/* Are pending spaces, then print them. There will be */
+	/* At most TAB-1 spaces to print.		      */
+	while (spaces > 0) {
+		putchar(' ');
+		--spaces;
+	}
+
+	if (c == '\n' || c == '\r') {
+		column = 0;
+		leading_blank = 1;
+		putchar(c);
+		continue;
+	}
+	if (c == '\b')
+		column = column > 0 ? column - 1 : 0;
+	else
+		++column;
+
+	leading_blank = 0;
+	putchar(c);
+  }
+}