sh(1): autocomplete commands

Without this patch, sh can autocomplete file names but not commands from
$PATH. Use libedit's facility to execute custom function for autocomplete,
but yield to the library's standard autocomplete function when cursor is
not at position 0.

Reviewed by:	bapt
Differential Revision:	https://reviews.freebsd.org/D29361

bin/sh/histedit.c

@@ -39,6 +39,8 @@ static char sccsid[] = "@(#)histedit.c	8.2 (Berkeley) 5/4/95";
 __FBSDID("$FreeBSD$");
 
 #include <sys/param.h>
+#include <sys/stat.h>
+#include <dirent.h>
 #include <limits.h>
 #include <paths.h>
 #include <stdio.h>
@@ -72,6 +74,9 @@ static FILE *el_in, *el_out;
 static char *fc_replace(const char *, char *, char *);
 static int not_fcnumber(const char *);
 static int str_to_event(const char *, int);
+static int comparator(const void *, const void *, void *);
+static char **sh_matches(const char *, int, int);
+static unsigned char sh_complete(EditLine *, int);
 
 /*
  * Set history and editing status.  Called whenever the status may
@@ -122,7 +127,7 @@ histedit(void)
 				el_set(el, EL_PROMPT, getprompt);
 				el_set(el, EL_ADDFN, "sh-complete",
 				    "Filename completion",
-				    _el_fn_complete);
+				    sh_complete);
 			} else {
 bad:
 				out2fmt_flush("sh: can't initialize editing\n");
@@ -519,3 +524,124 @@ bindcmd(int argc __unused, char **argv __unused)
 	return (0);
 }
 #endif
+
+/*
+ * Comparator function for qsort(). The use of curpos here is to skip
+ * characters that we already know to compare equal (common prefix).
+ */
+static int
+comparator(const void *a, const void *b, void *thunk)
+{
+	size_t curpos = (intptr_t)thunk;
+	return (strcmp(*(char *const *)a + curpos,
+		*(char *const *)b + curpos));
+}
+
+/*
+ * This function is passed to libedit's fn_complete2(). The library will
+ * use it instead of its standard function that finds matching files in
+ * current directory. If we're at the start of the line, we want to look
+ * for available commands from all paths in $PATH.
+ */
+static char
+**sh_matches(const char *text, int start, int end)
+{
+	char *free_path = NULL, *path;
+	const char *dirname;
+	char **matches = NULL;
+	size_t i = 0, size = 16, j, k;
+	size_t curpos = end - start;
+
+	if (start > 0 || memchr("/.~", text[0], 3) != NULL)
+		return (NULL);
+	if ((free_path = path = strdup(pathval())) == NULL)
+		goto out;
+	if ((matches = malloc(size * sizeof(matches[0]))) == NULL)
+		goto out;
+	while ((dirname = strsep(&path, ":")) != NULL) {
+		struct dirent *entry;
+		DIR *dir;
+		int dfd;
+
+		dir = opendir(dirname[0] == '\0' ? "." : dirname);
+		if (dir == NULL)
+			continue;
+		if ((dfd = dirfd(dir)) == -1) {
+			closedir(dir);
+			continue;
+		}
+		while ((entry = readdir(dir)) != NULL) {
+			struct stat statb;
+			char **rmatches;
+
+			if (strncmp(entry->d_name, text, curpos) != 0)
+				continue;
+			if (entry->d_type == DT_UNKNOWN || entry->d_type == DT_LNK) {
+				if (fstatat(dfd, entry->d_name, &statb, 0) == -1)
+					continue;
+				if (!S_ISREG(statb.st_mode))
+					continue;
+			} else if (entry->d_type != DT_REG)
+				continue;
+			matches[++i] = strdup(entry->d_name);
+			if (i < size - 1)
+				continue;
+			size *= 2;
+			rmatches = reallocarray(matches, size, sizeof(matches[0]));
+			if (rmatches == NULL) {
+				closedir(dir);
+				goto out;
+			}
+			matches = rmatches;
+		}
+		closedir(dir);
+	}
+out:
+	free(free_path);
+	/*
+	 * matches[0] is special: it's not a real matching file name but a common
+	 * prefix for all matching names. It can't be null, unlike any other
+	 * element of the array. When strings matches[0] and matches[1] compare
+	 * equal and matches[2] is null that means to libedit that there is only
+	 * a single match. It will then replace user input with possibly escaped
+	 * string in matches[0] which is the reason to copy the full name of the
+	 * only match.
+	 */
+	if (i == 0) {
+		free(matches);
+		return (NULL);
+	} else if (i == 1) {
+		matches[0] = strdup(matches[1]);
+		matches[2] = NULL;
+		if (matches[0] != NULL)
+			return (matches);
+	} else
+		matches[0] = strdup(text);
+	if (matches[0] == NULL) {
+		for (j = 1; j <= i; j++)
+			free(matches[j]);
+		free(matches);
+		return (NULL);
+	}
+	qsort_s(matches + 1, i, sizeof(matches[0]), comparator,
+		(void *)(intptr_t)curpos);
+	for (j = 1, k = 2; k <= i; k++)
+		if (strcmp(matches[j] + curpos, matches[k] + curpos) == 0)
+			free(matches[k]);
+		else
+			matches[++j] = matches[k];
+	matches[j + 1] = NULL;
+	return (matches);
+}
+
+/*
+ * This is passed to el_set(el, EL_ADDFN, ...) so that it's possible to
+ * bind a key (tab by default) to execute the function.
+ */
+unsigned char
+sh_complete(EditLine *sel, int ch __unused)
+{
+	return (unsigned char)fn_complete2(sel, NULL, sh_matches,
+		L" \t\n\"\\'`@$><=;|&{(", NULL, NULL, (size_t)100,
+		NULL, &((int) {0}), NULL, NULL, FN_QUOTE_MATCH);
+}

bin/sh/myhistedit.h

@@ -38,6 +38,8 @@ extern History *hist;
 extern EditLine *el;
 extern int displayhist;
 
+#include <filecomplete.h>
+
 void histedit(void);
 void sethistsize(const char *);
 void setterm(const char *);

lib/libedit/Makefile

@@ -65,7 +65,7 @@ MLINKS=	\
 	editline.3 tok_wreset.3 \
 	editline.3 tok_wstr.3
 
-INCS=	histedit.h
+INCS=	histedit.h filecomplete.h
 
 SRCS+=	common.h emacs.h fcns.h func.h help.h vi.h
 CLEANFILES+= common.h emacs.h fcns.h func.h help.h vi.h