diff -uraN st-0.8.5/autocomplete.h st-autocomplete/autocomplete.h
--- st-0.8.5/autocomplete.h	1970-01-01 04:00:00.000000000 +0400
+++ st-autocomplete/autocomplete.h	2022-03-13 02:45:34.586842452 +0400
@@ -0,0 +1,16 @@
+# ifndef __ST_AUTOCOMPLETE_H
+# define __ST_AUTOCOMPLETE_H
+
+enum {
+	ACMPL_DEACTIVATE,
+	ACMPL_WORD,
+	ACMPL_WWORD,
+	ACMPL_FUZZY_WORD,
+	ACMPL_FUZZY_WWORD,
+	ACMPL_FUZZY,
+	ACMPL_SUFFIX,
+	ACMPL_SURROUND,
+	ACMPL_UNDO,
+};
+
+# endif // __ST_AUTOCOMPLETE_H
diff -uraN st-0.8.5/config.def.h st-autocomplete/config.def.h
--- st-0.8.5/config.def.h	2022-03-13 02:45:34.586842452 +0400
+++ st-autocomplete/config.def.h	2022-03-13 02:45:34.586842452 +0400
@@ -170,6 +170,8 @@
  */
 static uint forcemousemod = ShiftMask;
 
+#include "autocomplete.h"
+
 /*
  * Internal mouse shortcuts.
  * Beware that overloading Button1 will disable the selection.
@@ -187,6 +189,8 @@
 #define MODKEY Mod1Mask
 #define TERMMOD (ControlMask|ShiftMask)
 
+#define ACMPL_MOD ControlMask|Mod1Mask
+
 static Shortcut shortcuts[] = {
 	/* mask                 keysym          function        argument */
 	{ XK_ANY_MOD,           XK_Break,       sendbreak,      {.i =  0} },
@@ -201,6 +205,14 @@
 	{ TERMMOD,              XK_Y,           selpaste,       {.i =  0} },
 	{ ShiftMask,            XK_Insert,      selpaste,       {.i =  0} },
 	{ TERMMOD,              XK_Num_Lock,    numlock,        {.i =  0} },
+	{ ACMPL_MOD,            XK_slash,       autocomplete,   { .i = ACMPL_WORD        } },
+	{ ACMPL_MOD,            XK_period,      autocomplete,   { .i = ACMPL_FUZZY_WORD  } },
+	{ ACMPL_MOD,            XK_comma,       autocomplete,   { .i = ACMPL_FUZZY       } },
+	{ ACMPL_MOD,            XK_apostrophe,  autocomplete,   { .i = ACMPL_SUFFIX      } },
+	{ ACMPL_MOD,            XK_semicolon,   autocomplete,   { .i = ACMPL_SURROUND    } },
+	{ ACMPL_MOD,            XK_bracketright,autocomplete,   { .i = ACMPL_WWORD       } },
+	{ ACMPL_MOD,            XK_bracketleft, autocomplete,   { .i = ACMPL_FUZZY_WWORD } },
+	{ ACMPL_MOD,            XK_equal,       autocomplete,   { .i = ACMPL_UNDO        } },
 };
 
 /*
diff -uraN st-0.8.5/Makefile st-autocomplete/Makefile
--- st-0.8.5/Makefile	2022-03-13 02:45:34.586842452 +0400
+++ st-autocomplete/Makefile	2022-03-13 02:45:34.586842452 +0400
@@ -44,6 +44,8 @@
 	mkdir -p $(DESTDIR)$(PREFIX)/bin
 	cp -f st $(DESTDIR)$(PREFIX)/bin
 	chmod 755 $(DESTDIR)$(PREFIX)/bin/st
+	cp -f st-autocomplete $(DESTDIR)$(PREFIX)/bin
+	chmod 755 $(DESTDIR)$(PREFIX)/bin/st-autocomplete
 	mkdir -p $(DESTDIR)$(MANPREFIX)/man1
 	sed "s/VERSION/$(VERSION)/g" < st.1 > $(DESTDIR)$(MANPREFIX)/man1/st.1
 	chmod 644 $(DESTDIR)$(MANPREFIX)/man1/st.1
@@ -52,6 +54,7 @@
 
 uninstall:
 	rm -f $(DESTDIR)$(PREFIX)/bin/st
+	rm -f $(DESTDIR)$(PREFIX)/bin/st-autocomplete
 	rm -f $(DESTDIR)$(MANPREFIX)/man1/st.1
 
 .PHONY: all options clean dist install uninstall
diff -uraN st-0.8.5/st-autocomplete st-autocomplete/st-autocomplete
--- st-0.8.5/st-autocomplete	1970-01-01 04:00:00.000000000 +0400
+++ st-autocomplete/st-autocomplete	2022-03-27 22:57:29.018288223 +0400
@@ -0,0 +1,310 @@
+#!/usr/bin/perl
+#########################################################################
+# Copyright (C) 2012-2017  Wojciech Siewierski                          #
+#                                                                       #
+# This program is free software: you can redistribute it and/or modify  #
+# it under the terms of the GNU General Public License as published by  #
+# the Free Software Foundation, either version 3 of the License, or     #
+# (at your option) any later version.                                   #
+#                                                                       #
+# This program is distributed in the hope that it will be useful,       #
+# but WITHOUT ANY WARRANTY; without even the implied warranty of        #
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         #
+# GNU General Public License for more details.                          #
+#                                                                       #
+# You should have received a copy of the GNU General Public License     #
+# along with this program.  If not, see <http://www.gnu.org/licenses/>. #
+#########################################################################
+
+my ($cmd, $cursor_row, $cursor_column) = @ARGV;
+
+my $lines = [];
+my $lines1 = [];
+
+my $last_line = -1;
+my $lines_before_cursor = 0;
+
+while (<stdin>)
+{
+	$last_line++;
+
+	s/[^[:print:]]/?/g;
+
+	if ($last_line < $cursor_row)
+	{
+		unshift @{$lines1}, $_;
+		$lines_before_cursor++;
+	}
+	else
+	{
+		unshift @{$lines}, $_;
+	}
+}
+
+foreach (@{$lines1})
+{
+	unshift @{$lines}, $_;
+}
+
+my $cursor_row_in = $cursor_row;
+
+$cursor_row = $last_line;
+
+
+$self = {};
+
+# A reference to a function that transforms the completed word
+# into a regex matching the completions. Usually generated by
+# generate_matcher().
+#
+# For example
+#   $fun = generate_matcher(".*");
+#   $fun->("foo");
+# would return "f.*o.*o"
+#
+# In other words, indirectly decides which characters can
+# appear in the completion.
+my $matcher;
+
+# A regular expression matching a character before each match.
+# For example, it you want to match the text after a
+# whitespace, set it to "\s".
+my $char_class_before;
+
+# A regular expression matching every character in the entered
+# text that will be used to find matching completions. Usually
+# "\w" or similar.
+my $char_class_to_complete;
+
+# A regular expression matching every allowed last character
+# of the completion (uses greedy matching).
+my $char_class_at_end;
+
+if ($cmd eq 'word-complete') {
+	# Basic word completion. Completes the current word
+	# without any special matching.
+	$char_class_before      = '[^-\w]';
+	$matcher                = sub { quotemeta shift }; # identity
+	$char_class_at_end      = '[-\w]';
+	$char_class_to_complete = '[-\w]';
+} elsif ($cmd eq 'WORD-complete') {
+	# The same as above but in the Vim meaning of a "WORD" --
+	# whitespace delimited.
+	$char_class_before      = '\s';
+	$matcher                = sub { quotemeta shift };
+	$char_class_at_end      = '\S';
+	$char_class_to_complete = '\S';
+} elsif ($cmd eq 'fuzzy-word-complete' ||
+		 $cmd eq 'skeleton-word-complete') {
+	# Fuzzy completion of the current word.
+	$char_class_before      = '[^-\w]';
+	$matcher                = generate_matcher('[-\w]*');
+	$char_class_at_end      = '[-\w]';
+	$char_class_to_complete = '[-\w]';
+} elsif ($cmd eq 'fuzzy-WORD-complete') {
+	# Fuzzy completion of the current WORD.
+	$char_class_before      = '\s';
+	$matcher                = generate_matcher('\S*');
+	$char_class_at_end      = '\S';
+	$char_class_to_complete = '\S';
+} elsif ($cmd eq 'fuzzy-complete' ||
+		 $cmd eq 'skeleton-complete') {
+	# Fuzzy completion of an arbitrary text.
+	$char_class_before      = '\W';
+	$matcher                = generate_matcher('.*?');
+	$char_class_at_end      = '\w';
+	$char_class_to_complete = '\S';
+} elsif ($cmd eq 'suffix-complete') {
+	# Fuzzy completion of an completing suffixes, like
+	# completing test=hello from /blah/hello.
+	$char_class_before      = '\S';
+	$matcher                = generate_matcher('\S*');
+	$char_class_at_end      = '\S';
+	$char_class_to_complete = '\S';
+} elsif ($cmd eq 'surround-complete') {
+	# Completing contents of quotes and braces.
+
+	# Here we are using three named groups: s, b, p for quotes, braces
+	# and parenthesis.
+	$char_class_before      = '((?<q>["\'`])|(?<b>\[)|(?<p>\())';
+
+	$matcher                = generate_matcher('.*?');
+
+	# Here we match text till enclosing pair, using perl conditionals in
+	# regexps (?(condition)yes-expression|no-expression).
+	# \0 is used to hack concatenation with '*' later in the code.
+	$char_class_at_end      = '.*?(.(?=(?(<b>)\]|((?(<p>)\)|\g{q})))))\0';
+	$char_class_to_complete = '\S';
+}
+
+
+# use the last used word or read the word behind the cursor
+my $word_to_complete = read_word_at_coord($self, $cursor_row, $cursor_column,
+										  $char_class_to_complete);
+
+print stdout "$word_to_complete\n";
+
+if ($word_to_complete) {
+	while (1) {
+		# ignore the completed word itself
+		$self->{already_completed}{$word_to_complete} = 1;
+
+		# continue the last search or start from the current row
+		my $completion = find_match($self,
+									$word_to_complete,
+									$self->{next_row} // $cursor_row,
+									$matcher->($word_to_complete),
+									$char_class_before,
+									$char_class_at_end);
+		if ($completion) {
+			print stdout $completion."\n".join ("\n", @{$self->{highlight}})."\n";
+		}
+		else {
+			last;
+		}
+	}
+}
+
+######################################################################
+
+sub highlight_match {
+    my ($self, $linenum, $completion) = @_;
+
+    # clear_highlight($self);
+
+    my $line = @{$lines}[$linenum];
+    my $re = quotemeta $completion;
+
+    $line =~ /$re/;
+
+    my $beg = $-[0];
+    my $end = $+[0];
+
+	if ($linenum >= $lines_before_cursor)
+	{
+		$lline = $last_line - $lines_before_cursor;
+		$linenum -= $lines_before_cursor;
+		$linenum = $lline - $linenum;
+		$linenum += $lines_before_cursor;
+	}
+
+
+    $self->{highlight} = [$linenum, $beg, $end];
+}
+
+######################################################################
+
+sub read_word_at_coord {
+    my ($self, $row, $col, $char_class) = @_;
+
+    $_ = substr(@{$lines} [$row], 0, $col); # get the current line up to the cursor...
+    s/.*?($char_class*)$/$1/;               # ...and read the last word from it
+    return $_;
+}
+
+######################################################################
+
+# Returns a function that takes a string and returns that string with
+# this function's argument inserted between its every two characters.
+# The resulting string is used as a regular expression matching the
+# completion candidates.
+sub generate_matcher {
+    my $regex_between = shift;
+
+    sub {
+        $_ = shift;
+
+        # sorry for this lispy code, I couldn't resist ;)
+        (join "$regex_between",
+         (map quotemeta,
+          (split //)))
+    }
+}
+
+######################################################################
+
+# Checks whether the completion found by find_match() was already
+# found and if it was, calls find_match() again to find the next
+# completion.
+#
+# Takes all the arguments that find_match() would take, to make a
+# mutually recursive call.
+sub skip_duplicates {
+    my ($self, $word_to_match, $current_row, $regexp, $char_class_before, $char_class_at_end) = @_;
+    my $completion;
+
+	if ($current_row <= $lines_before_cursor)
+	{
+		$completion = shift @{$self->{matches_in_row}}; # get the leftmost one
+	}
+	else
+	{
+		$completion = pop @{$self->{matches_in_row}}; # get the leftmost one
+	}
+
+    # check for duplicates
+    if (exists $self->{already_completed}{$completion}) {
+        # skip this completion
+        return find_match(@_);
+    } else {
+        $self->{already_completed}{$completion} = 1;
+
+		highlight_match($self,
+						$self->{next_row}+1,
+						$completion);
+
+        return $completion;
+    }
+}
+
+######################################################################
+
+# Finds the next matching completion in the row current row or above
+# while skipping duplicates using skip_duplicates().
+sub find_match {
+    my ($self, $word_to_match, $current_row, $regexp, $char_class_before, $char_class_at_end) = @_;
+    $self->{matches_in_row} //= [];
+
+    # cycle through all the matches in the current row if not starting a new search
+    if (@{$self->{matches_in_row}}) {
+        return skip_duplicates($self, $word_to_match, $current_row, $regexp, $char_class_before, $char_class_at_end);
+    }
+
+
+    my $i;
+    # search through all the rows starting with current one or one above the last checked
+    for ($i = $current_row; $i >= 0; --$i) {
+        my $line = @{$lines}[$i];   # get the line of text from the row
+
+        # if ($i == $cursor_row) {
+        #     $line = substr $line, 0, $cursor_column;
+        # }
+
+        $_ = $line;
+
+        # find all the matches in the current line
+        my $match;
+        push @{$self->{matches_in_row}}, $+{match} while ($_, $match) = /
+                                                                         (.*${char_class_before})
+                                                                         (?<match>
+                                                                             ${regexp}
+                                                                             ${char_class_at_end}*
+                                                                         )
+                                                                     /ix;
+        # corner case: match at the very beginning of line
+        push @{$self->{matches_in_row}}, $+{match} if $line =~ /^(${char_class_before}){0}(?<match>$regexp$char_class_at_end*)/i;
+
+        if (@{$self->{matches_in_row}}) {
+            # remember which row should be searched next
+            $self->{next_row} = --$i;
+
+            # arguments needed for find_match() mutual recursion
+            return skip_duplicates($self, $word_to_match, $i, $regexp, $char_class_before, $char_class_at_end);
+        }
+    }
+
+    # # no more possible completions, revert to the original word
+    # undo_completion($self) if $i < 0;
+
+    return undef;
+}
diff -uraN st-0.8.5/st.c st-autocomplete/st.c
--- st-0.8.5/st.c	2022-03-13 02:45:34.586842452 +0400
+++ st-autocomplete/st.c	2022-03-27 22:28:39.041693478 +0400
@@ -17,6 +17,7 @@
 #include <unistd.h>
 #include <wchar.h>
 
+#include "autocomplete.h"
 #include "st.h"
 #include "win.h"
 
@@ -2569,6 +2570,8 @@
 		return;
 	}
 
+	autocomplete ((const Arg []) { ACMPL_DEACTIVATE });
+
 	/*
 	 * slide screen to keep cursor where we expect it -
 	 * tscrollup would work here, but we can optimize to
@@ -2688,3 +2691,256 @@
 	tfulldirt();
 	draw();
 }
+
+void autocomplete (const Arg * arg)
+{
+	static _Bool active = 0;
+
+	int acmpl_cmdindex = arg -> i;
+
+	static int acmpl_cmdindex_prev;
+
+	if (active == 0)
+		acmpl_cmdindex_prev = acmpl_cmdindex;
+
+	static const char * const (acmpl_cmd []) = {
+		[ACMPL_DEACTIVATE]	= "__DEACTIVATE__",
+		[ACMPL_WORD]		= "word-complete",
+		[ACMPL_WWORD]		= "WORD-complete",
+		[ACMPL_FUZZY_WORD]	= "fuzzy-word-complete",
+		[ACMPL_FUZZY_WWORD]	= "fuzzy-WORD-complete",
+		[ACMPL_FUZZY]		= "fuzzy-complete",
+		[ACMPL_SUFFIX]		= "suffix-complete",
+		[ACMPL_SURROUND]	= "surround-complete",
+		[ACMPL_UNDO]		= "__UNDO__",
+	};
+
+	static char acmpl [1000];		// ACMPL_ISSUE: why 1000?
+
+	static FILE * acmpl_exec = NULL;
+	static int acmpl_status;
+
+	static const char * stbuffile;
+	static char target [1000];		// ACMPL_ISSUE: why 1000? dynamically allocate char array of size term.col
+	static size_t targetlen;
+
+	static char completion [1000] = {0};		// ACMPL_ISSUE: why 1000? dynamically allocate char array of size term.col
+	static size_t complen_prev = 0;		// NOTE: always clear this variable after clearing completion
+
+	static int cx, cy;
+
+	// ACMPL_ISSUE: crashes when term.row is too small
+
+// Check for deactivation
+
+	if (acmpl_cmdindex == ACMPL_DEACTIVATE)
+	{
+
+//     Deactivate autocomplete mode keeping current completion
+
+		if (active)
+		{
+			active = 0;
+			pclose (acmpl_exec);
+			remove (stbuffile);
+
+			if (complen_prev)
+			{
+				selclear ();
+				complen_prev = 0;
+			}
+		}
+
+		return;
+	}
+
+// Check for undo
+
+	if (acmpl_cmdindex == ACMPL_UNDO)
+	{
+
+//     Deactivate autocomplete mode recovering target
+
+		if (active)
+		{
+			active = 0;
+			pclose (acmpl_exec);
+			remove (stbuffile);
+
+			if (complen_prev)
+			{
+				selclear ();
+				for (size_t i = 0; i < complen_prev; i++)
+					ttywrite ((char []) { '\b' }, 1, 1);	// ACMPL_ISSUE: I'm not sure that this is the right way
+				complen_prev = 0;
+				ttywrite (target, targetlen, 0);		// ACMPL_ISSUE: I'm not sure that this is a right solution
+			}
+		}
+
+		return;
+	}
+
+// Check for command change
+
+	if (acmpl_cmdindex != acmpl_cmdindex_prev)
+	{
+
+//     If command is changed, goto acmpl_begin avoiding rewriting st buffer
+
+		if (active)
+		{
+			acmpl_cmdindex_prev = acmpl_cmdindex;
+
+			goto acmpl_begin;
+		}
+	}
+
+// If not active
+
+	if (active == 0)
+	{
+		acmpl_cmdindex_prev = acmpl_cmdindex;
+		cx = term.c.x;
+		cy = term.c.y;
+
+//     Write st buffer to a temp file
+
+		stbuffile = tmpnam (NULL);		// ACMPL_ISSUE: check for return value ...
+										// ACMPL_ISSUE: use coprocesses instead of temp files
+
+		FILE * stbuf = fopen (stbuffile, "w"); // ACMPL_ISSUE: check for opening error ...
+		char * stbufline = malloc (term.col + 2); // ACMPL_ISSUE: check for allocating error ...
+
+		int cxp = 0;
+
+		for (size_t y = 0; y < term.row; y++)
+		{
+			if (y == term.c.y) cx += cxp * term.col;
+
+			size_t x = 0;
+			for (; x < term.col; x++)
+				utf8encode (term.line [y] [x].u, stbufline + x);
+			if (term.line [y] [x - 1].mode & ATTR_WRAP)
+			{
+				x--;
+				if (y <= term.c.y) cy--;
+				cxp++;
+			}
+			else
+			{
+				stbufline [x] = '\n';
+				cxp = 0;
+			}
+			stbufline [x + 1] = 0;
+			fputs (stbufline, stbuf);
+		}
+
+		free (stbufline);
+		fclose (stbuf);
+
+acmpl_begin:
+
+//     Run st-autocomplete
+
+		sprintf (
+			acmpl,
+			"cat %100s | st-autocomplete %500s %d %d",	// ACMPL_ISSUE: why 100 and 500?
+			stbuffile,
+			acmpl_cmd [acmpl_cmdindex],
+			cy,
+			cx
+		);
+
+		acmpl_exec = popen (acmpl, "r");		// ACMPL_ISSUE: popen isn't defined by The Standard. Does it work in BSDs for example?
+												// ACMPL_ISSUE: check for popen error ...
+
+//     Read the target, targetlen
+
+		fscanf (acmpl_exec, "%500s\n", target); // ACMPL_ISSUE: check for scanning error ...
+		targetlen = strlen (target);
+	}
+
+// Read a completion if exists (acmpl_status)
+
+	unsigned line, beg, end;
+
+	acmpl_status = fscanf (acmpl_exec, "%500[^\n]\n%u\n%u\n%u\n", completion, & line, & beg, & end);
+												// ACMPL_ISSUE: why 500? use term.col instead
+
+// Exit if no completions found
+
+	if (active == 0 && acmpl_status == EOF)
+	{
+
+//    Close st-autocomplete and exit without activating the autocomplete mode
+
+		pclose (acmpl_exec);
+		remove (stbuffile);
+		return;
+	}
+
+// If completions found, enable autocomplete mode and autocomplete the target
+
+	active = 1;
+
+// Clear target before first completion
+
+	if (complen_prev == 0)
+	{
+		for (size_t i = 0; i < targetlen; i++)
+			ttywrite ((char []) { '\b' }, 1, 1);	// ACMPL_ISSUE: I'm not sure that this is a right solution
+	}
+
+// Clear previuos completion if this is not the first
+
+	else
+	{
+		selclear ();
+		for (size_t i = 0; i < complen_prev; i++)
+			ttywrite ((char []) { '\b' }, 1, 1);	// ACMPL_ISSUE: I'm not sure that this is a right solution
+		complen_prev = 0;
+	}
+
+// If no more completions found, reset and restart
+
+	if (acmpl_status == EOF)
+	{
+		active = 0;
+		pclose (acmpl_exec);
+		ttywrite (target, targetlen, 0);
+		goto acmpl_begin;
+	}
+
+// Count wrapped lines before the current line
+
+	int wl = 0;
+
+	int tl = line;
+
+	for (int l = 0; l < tl; l++)
+		if (term.line [l] [term.col - 1].mode & ATTR_WRAP)
+		{
+			wl++;
+			tl++;
+		}
+
+// Autcomplete
+
+	complen_prev = strlen (completion);
+	ttywrite (completion, complen_prev, 0);
+
+	if (line == cy && beg > cx)
+	{
+		beg += complen_prev - targetlen;
+		end += complen_prev - targetlen;
+
+		// ACMPL_ISSUE: highlignthing doesn't work when "line == cy && beg > cx",
+		//				but coordinates are correct...
+	}
+
+	end--;
+
+	selstart (beg % term.col, line + wl + beg / term.col, 0);
+	selextend (end % term.col, line + wl + end / term.col, 1, 0);
+	xsetsel (getsel ());
+}
diff -uraN st-0.8.5/st.h st-autocomplete/st.h
--- st-0.8.5/st.h	2022-03-13 02:45:34.586842452 +0400
+++ st-autocomplete/st.h	2022-03-13 02:45:34.586842452 +0400
@@ -77,6 +77,8 @@
 	const char *s;
 } Arg;
 
+void autocomplete (const Arg *);
+
 void die(const char *, ...);
 void redraw(void);
 void draw(void);
diff -uraN st-0.8.5/x.c st-autocomplete/x.c
--- st-0.8.5/x.c	2022-03-13 02:45:34.586842452 +0400
+++ st-autocomplete/x.c	2022-03-13 02:45:34.590175835 +0400
@@ -1834,11 +1834,20 @@
 	/* 1. shortcuts */
 	for (bp = shortcuts; bp < shortcuts + LEN(shortcuts); bp++) {
 		if (ksym == bp->keysym && match(bp->mod, e->state)) {
+			if (bp -> func != autocomplete)
+				autocomplete ((const Arg []) { ACMPL_DEACTIVATE });
 			bp->func(&(bp->arg));
 			return;
 		}
 	}
 
+	if (!(
+		len == 0 &&
+		e -> state & ~ignoremod		// ACMPL_ISSUE: I'm not sure that this is the right way
+				| ACMPL_MOD == ACMPL_MOD
+	))
+		autocomplete ((const Arg []) { ACMPL_DEACTIVATE });
+
 	/* 2. custom keys from config.h */
 	if ((customkey = kmap(ksym, e->state))) {
 		ttywrite(customkey, strlen(customkey), 1);
