diff --git a/.gitignore b/.gitignore
index 3befbcd..3489b97 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@ Makefile
 autom4te.cache
 config.log
 config.status
+local.env
 release-checklist.txt
 shell-toolbox-*.tar.gz
 src/shell
diff --git a/INSTALL b/INSTALL
index ceb83c7..923275b 100644
--- a/INSTALL
+++ b/INSTALL
@@ -1,48 +1,60 @@
-This project uses GNU autotools.
-
-To install the scripts under "/usr/local" (scripts will always go in the
-"bin" subdirectory):
-
-    ./configure
-    make
-    make install
-
-Then make sure that "/usr/local/bin" is in your "$PATH".
-
-To install under "$HOME/local":
-
-    ./configure --prefix="$HOME/local"
-    make
-    make install
-
-To install using GNU Stow under "$HOME/local":
-
-    ./configure --prefix="$HOME/local/stow/shell-toolbox"
-    make
-    make install
-    cd "$HOME/local/stow"
-    stow shell-toolbox
-
-Then make sure that "$HOME/local/bin" is in your "$PATH".
-
-The following files will be installed unless the default installation
-paths are modified:
-
-    <prefix>
-    |-- bin
-    |   `-- shell
-    `-- share
-        |-- doc
-        |   `-- shell-toolbox
-        |       |-- LICENSE
-        |       |-- NEWS
-        |       |-- README
-        |       |-- shell.md
-        |       `-- shell.txt
-        `-- man
-            `-- man1
-                `-- shell.1
-
-Caveat: If you run "make distclean", the generated manuals, which are
-part of the distribution sources, will be removed.  These won't be
-rebuilt unless you have mandoc(1) installed.
+1. Installing from the distribution tar archive or a GitHub clone:
+
+    This project uses GNU autotools.
+
+    To install the scripts under "/usr/local" (scripts will always go in
+    the "bin" subdirectory):
+
+        ./configure
+        make
+        make install
+
+    Then make sure that "/usr/local/bin" is in your "$PATH".
+
+    To install under "$HOME/local":
+
+        ./configure --prefix="$HOME/local"
+        make
+        make install
+
+    To install using GNU Stow under "$HOME/local":
+
+        ./configure --prefix="$HOME/local/stow/shell-toolbox"
+        make
+        make install
+        cd "$HOME/local/stow"
+        stow shell-toolbox
+
+    Then make sure that "$HOME/local/bin" is in your "$PATH".
+
+    The following files will be installed unless the default
+    installation paths are modified:
+
+        <prefix>
+        |-- bin
+        |   `-- shell
+        `-- share
+            |-- doc
+            |   `-- shell-toolbox
+            |       |-- LICENSE
+            |       |-- NEWS
+            |       |-- README
+            |       |-- shell.md
+            |       `-- shell.txt
+            `-- man
+                `-- man1
+                    `-- shell.1
+
+    Caveat: If you run "make distclean", the generated manuals, which
+    are part of the distribution sources, will be removed.  These won't
+    be rebuilt unless you have mandoc(1) installed.
+
+2. Installing on FreeBSD:
+
+    The devel/shell-toolbox port:
+
+        cd /usr/ports/devel/shell-toolbox/ && make install clean
+
+    The shell-toolbox package:
+
+        pkg install shell-toolbox
diff --git a/Makefile.in b/Makefile.in
index f3a0481..587090a 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -252,7 +252,6 @@ LTLIBOBJS = @LTLIBOBJS@
 MAINT = @MAINT@
 MAKEINFO = @MAKEINFO@
 MANDOC = @MANDOC@
-MANDOC_DOES_MARKDOWN = @MANDOC_DOES_MARKDOWN@
 MKDIR_P = @MKDIR_P@
 MKTEMP = @MKTEMP@
 MKTEMP_TEMPLATE = @MKTEMP_TEMPLATE@
diff --git a/NEWS b/NEWS
index 74cd3dd..49fe04e 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,11 @@
+Release 20180719
+    * A skeleton directory (to pre-populate the temporary working
+      directory with) may be specified by setting the SHELL_SKEL
+      environment variable to the path of a directory.  This environment
+      variable is not used if the command line option -s or -d is used.
+    * /bin/sh is used if SHELL is empty or unset and no other shell is
+      specified.
+
 Release 20180422
     * Added NEWS file.
     * Added -q option for quiet operation.
diff --git a/TODO b/TODO
index 5ec7406..44640fd 100644
--- a/TODO
+++ b/TODO
@@ -2,4 +2,6 @@
       This will not happen until the toolbox contains more than a single
       script.
 
+    * Write the shell code formatter script/program.
+
     * shell:    Nothing at the moment.
diff --git a/aclocal.m4 b/aclocal.m4
index c0f7c1a..60d8fe6 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -108,6 +108,43 @@ AC_DEFUN([AM_AUX_DIR_EXPAND],
 am_aux_dir=`cd "$ac_aux_dir" && pwd`
 ])
 
+# AM_COND_IF                                            -*- Autoconf -*-
+
+# Copyright (C) 2008-2018 Free Software Foundation, Inc.
+#
+# This file is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# _AM_COND_IF
+# _AM_COND_ELSE
+# _AM_COND_ENDIF
+# --------------
+# These macros are only used for tracing.
+m4_define([_AM_COND_IF])
+m4_define([_AM_COND_ELSE])
+m4_define([_AM_COND_ENDIF])
+
+# AM_COND_IF(COND, [IF-TRUE], [IF-FALSE])
+# ---------------------------------------
+# If the shell condition COND is true, execute IF-TRUE, otherwise execute
+# IF-FALSE.  Allow automake to learn about conditional instantiating macros
+# (the AC_CONFIG_FOOS).
+AC_DEFUN([AM_COND_IF],
+[m4_ifndef([_AM_COND_VALUE_$1],
+	   [m4_fatal([$0: no such condition "$1"])])dnl
+_AM_COND_IF([$1])dnl
+if test -z "$$1_TRUE"; then :
+  m4_n([$2])[]dnl
+m4_ifval([$3],
+[_AM_COND_ELSE([$1])dnl
+else
+  $3
+])dnl
+_AM_COND_ENDIF([$1])dnl
+fi[]dnl
+])
+
 # AM_CONDITIONAL                                            -*- Autoconf -*-
 
 # Copyright (C) 1997-2018 Free Software Foundation, Inc.
diff --git a/configure b/configure
index 1582a76..007ca1f 100755
--- a/configure
+++ b/configure
@@ -1,6 +1,6 @@
 #! /bin/sh
 # Guess values for system-dependent variables and create Makefiles.
-# Generated by GNU Autoconf 2.69.195-487d6 for shell-toolbox 20180422.
+# Generated by GNU Autoconf 2.69.195-487d6 for shell-toolbox 20180719.
 #
 # Report bugs to <https://github.com/kusalananda/shell-toolbox/issues>.
 #
@@ -565,17 +565,18 @@ MAKEFLAGS=
 # Identity of this package.
 PACKAGE_NAME='shell-toolbox'
 PACKAGE_TARNAME='shell-toolbox'
-PACKAGE_VERSION='20180422'
-PACKAGE_STRING='shell-toolbox 20180422'
+PACKAGE_VERSION='20180719'
+PACKAGE_STRING='shell-toolbox 20180719'
 PACKAGE_BUGREPORT='https://github.com/kusalananda/shell-toolbox/issues'
 PACKAGE_URL=''
 
 ac_unique_file="src/shell.in"
 ac_subst_vars='LTLIBOBJS
 LIBOBJS
-MANDOC_DOES_MARKDOWN
-MANDOC
+BUILD_MANUALS_FALSE
+BUILD_MANUALS_TRUE
 COL
+MANDOC
 MKTEMP_TEMPLATE
 MKTEMP
 MAINT
@@ -1206,7 +1207,7 @@ if test "$ac_init_help" = "long"; then
   # Omit some internal or obsolete options to make the list less imposing.
   # This message is too long to be a string in the A/UX 3.1 sh.
   cat <<_ACEOF
-\`configure' configures shell-toolbox 20180422 to adapt to many kinds of systems.
+\`configure' configures shell-toolbox 20180719 to adapt to many kinds of systems.
 
 Usage: $0 [OPTION]... [VAR=VALUE]...
 
@@ -1273,7 +1274,7 @@ fi
 
 if test -n "$ac_init_help"; then
   case $ac_init_help in
-     short | recursive ) echo "Configuration of shell-toolbox 20180422:";;
+     short | recursive ) echo "Configuration of shell-toolbox 20180719:";;
    esac
   cat <<\_ACEOF
 
@@ -1350,7 +1351,7 @@ fi
 test -n "$ac_init_help" && exit $ac_status
 if $ac_init_version; then
   cat <<\_ACEOF
-shell-toolbox configure 20180422
+shell-toolbox configure 20180719
 generated by GNU Autoconf 2.69.195-487d6
 
 Copyright (C) 2017 Free Software Foundation, Inc.
@@ -1387,7 +1388,7 @@ cat >config.log <<_ACEOF
 This file contains any messages produced by compilers while
 running configure, to aid debugging if configure makes a mistake.
 
-It was created by shell-toolbox $as_me 20180422, which was
+It was created by shell-toolbox $as_me 20180719, which was
 generated by GNU Autoconf 2.69.195-487d6.  Invocation command line was
 
   $ $0$ac_configure_args_raw
@@ -2275,7 +2276,7 @@ fi
 
 # Define the identity of the package.
  PACKAGE='shell-toolbox'
- VERSION='20180422'
+ VERSION='20180719'
 
 
 printf "%s\n" "#define PACKAGE \"$PACKAGE\"" >>confdefs.h
@@ -2468,17 +2469,17 @@ fi
 # distributed manuals are ever deleted (e.g. using "make distclean") or
 # if the source manual sources are updated. col is used for generating
 # the text-only version of the manuals.
-# Extract the first word of "col", so it can be a program name with args.
-set dummy col; ac_word=$2
+# Extract the first word of "mandoc", so it can be a program name with args.
+set dummy mandoc; ac_word=$2
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
 printf %s "checking for $ac_word... " >&6; }
-if test ${ac_cv_path_COL+y}
+if test ${ac_cv_path_MANDOC+y}
 then :
   printf %s "(cached) " >&6
 else
-  case $COL in
+  case $MANDOC in
   [\\/]* | ?:[\\/]*)
-  ac_cv_path_COL="$COL" # Let the user override the test with a path.
+  ac_cv_path_MANDOC="$MANDOC" # Let the user override the test with a path.
   ;;
   *)
   as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
@@ -2492,7 +2493,7 @@ do
   esac
     for ac_exec_ext in '' $ac_executable_extensions; do
   if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
-    ac_cv_path_COL="$as_dir$ac_word$ac_exec_ext"
+    ac_cv_path_MANDOC="$as_dir$ac_word$ac_exec_ext"
     printf "%s\n" "$as_me:${as_lineno-$LINENO}: found $as_dir$ac_word$ac_exec_ext" >&5
     break 2
   fi
@@ -2503,27 +2504,27 @@ IFS=$as_save_IFS
   ;;
 esac
 fi
-COL=$ac_cv_path_COL
-if test -n "$COL"; then
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $COL" >&5
-printf "%s\n" "$COL" >&6; }
+MANDOC=$ac_cv_path_MANDOC
+if test -n "$MANDOC"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $MANDOC" >&5
+printf "%s\n" "$MANDOC" >&6; }
 else
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
 printf "%s\n" "no" >&6; }
 fi
 
 
-# Extract the first word of "mandoc", so it can be a program name with args.
-set dummy mandoc; ac_word=$2
+# Extract the first word of "col", so it can be a program name with args.
+set dummy col; ac_word=$2
 { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
 printf %s "checking for $ac_word... " >&6; }
-if test ${ac_cv_path_MANDOC+y}
+if test ${ac_cv_path_COL+y}
 then :
   printf %s "(cached) " >&6
 else
-  case $MANDOC in
+  case $COL in
   [\\/]* | ?:[\\/]*)
-  ac_cv_path_MANDOC="$MANDOC" # Let the user override the test with a path.
+  ac_cv_path_COL="$COL" # Let the user override the test with a path.
   ;;
   *)
   as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
@@ -2537,7 +2538,7 @@ do
   esac
     for ac_exec_ext in '' $ac_executable_extensions; do
   if as_fn_executable_p "$as_dir$ac_word$ac_exec_ext"; then
-    ac_cv_path_MANDOC="$as_dir$ac_word$ac_exec_ext"
+    ac_cv_path_COL="$as_dir$ac_word$ac_exec_ext"
     printf "%s\n" "$as_me:${as_lineno-$LINENO}: found $as_dir$ac_word$ac_exec_ext" >&5
     break 2
   fi
@@ -2548,32 +2549,49 @@ IFS=$as_save_IFS
   ;;
 esac
 fi
-MANDOC=$ac_cv_path_MANDOC
-if test -n "$MANDOC"; then
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $MANDOC" >&5
-printf "%s\n" "$MANDOC" >&6; }
+COL=$ac_cv_path_COL
+if test -n "$COL"; then
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $COL" >&5
+printf "%s\n" "$COL" >&6; }
 else
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
 printf "%s\n" "no" >&6; }
 fi
 
 
-if test -n "$MANDOC"
-then :
+ if test -n "$MANDOC" && test -n "$COL"; then
+  BUILD_MANUALS_TRUE=
+  BUILD_MANUALS_FALSE='#'
+else
+  BUILD_MANUALS_TRUE='#'
+  BUILD_MANUALS_FALSE=
+fi
+
+
+if test -z "$BUILD_MANUALS_TRUE"; then :
   { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether $MANDOC can produce markdown output" >&5
 printf %s "checking whether $MANDOC can produce markdown output... " >&6; }
-      if "$MANDOC" -T markdown </dev/null 2>/dev/null
-then :
-  MANDOC_DOES_MARKDOWN=yes
+       if "$MANDOC" -T markdown </dev/null 2>/dev/null; then
+  BUILD_MANUALS_TRUE=
+  BUILD_MANUALS_FALSE='#'
 else
-  MANDOC_DOES_MARKDOWN=no
+  BUILD_MANUALS_TRUE='#'
+  BUILD_MANUALS_FALSE=
 fi
-      { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: $MANDOC_DOES_MARKDOWN" >&5
-printf "%s\n" "$MANDOC_DOES_MARKDOWN" >&6; }
 
+      if test -z "$BUILD_MANUALS_TRUE"; then :
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: yes" >&5
+printf "%s\n" "yes" >&6; }
 else
-  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: mandoc is missing, manuals can not be rebuilt" >&5
-printf "%s\n" "$as_me: WARNING: mandoc is missing, manuals can not be rebuilt" >&2;}
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: result: no" >&5
+printf "%s\n" "no" >&6; }
+fi
+fi
+
+if test -z "$BUILD_MANUALS_TRUE"; then :
+  else
+  { printf "%s\n" "$as_me:${as_lineno-$LINENO}: WARNING: col or usable mandoc is missing, manuals can not be rebuilt" >&5
+printf "%s\n" "$as_me: WARNING: col or usable mandoc is missing, manuals can not be rebuilt" >&2;}
 fi
 
 ac_config_files="$ac_config_files Makefile src/Makefile doc/Makefile"
@@ -2738,6 +2756,14 @@ if test -z "${MAINTAINER_MODE_TRUE}" && test -z "${MAINTAINER_MODE_FALSE}"; then
   as_fn_error $? "conditional \"MAINTAINER_MODE\" was never defined.
 Usually this means the macro was only invoked conditionally." "$LINENO" 5
 fi
+if test -z "${BUILD_MANUALS_TRUE}" && test -z "${BUILD_MANUALS_FALSE}"; then
+  as_fn_error $? "conditional \"BUILD_MANUALS\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
+if test -z "${BUILD_MANUALS_TRUE}" && test -z "${BUILD_MANUALS_FALSE}"; then
+  as_fn_error $? "conditional \"BUILD_MANUALS\" was never defined.
+Usually this means the macro was only invoked conditionally." "$LINENO" 5
+fi
 
 : "${CONFIG_STATUS=./config.status}"
 ac_write_fail=0
@@ -3107,7 +3133,7 @@ cat >>$CONFIG_STATUS <<\_ACEOF || ac_write_fail=1
 # report actual input values of CONFIG_FILES etc. instead of their
 # values after options handling.
 ac_log="
-This file was extended by shell-toolbox $as_me 20180422, which was
+This file was extended by shell-toolbox $as_me 20180719, which was
 generated by GNU Autoconf 2.69.195-487d6.  Invocation command line was
 
   CONFIG_FILES    = $CONFIG_FILES
@@ -3162,7 +3188,7 @@ ac_cs_config_escaped=`printf "%s\n" "$ac_cs_config" | sed "s/^ //; s/'/'\\\\\\\\
 cat >>$CONFIG_STATUS <<_ACEOF || ac_write_fail=1
 ac_cs_config='$ac_cs_config_escaped'
 ac_cs_version="\\
-shell-toolbox config.status 20180422
+shell-toolbox config.status 20180719
 configured by $0, generated by GNU Autoconf 2.69.195-487d6,
   with options \\"\$ac_cs_config\\"
 
diff --git a/configure.ac b/configure.ac
index 77dd0bb..38b4fa7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1,6 +1,5 @@
 AC_PREREQ([2.69])
-AC_INIT([shell-toolbox],[20180422],
-        [https://github.com/kusalananda/shell-toolbox/issues])
+AC_INIT([shell-toolbox],[20180719],[https://github.com/kusalananda/shell-toolbox/issues])
 
 AC_CONFIG_AUX_DIR([build])
 
@@ -33,16 +32,20 @@ AS_IF([test -n "$MKTEMP"],
 # distributed manuals are ever deleted (e.g. using "make distclean") or
 # if the source manual sources are updated. col is used for generating
 # the text-only version of the manuals.
-AC_PATH_PROG(COL, [col])
 AC_PATH_PROG(MANDOC, [mandoc])
-AS_IF([test -n "$MANDOC"],
+AC_PATH_PROG(COL, [col])
+AM_CONDITIONAL([BUILD_MANUALS], [test -n "$MANDOC" && test -n "$COL"])
+
+AM_COND_IF([BUILD_MANUALS],
       [AC_MSG_CHECKING([whether $MANDOC can produce markdown output])
-      AS_IF(["$MANDOC" -T markdown </dev/null 2>/dev/null],
-            [MANDOC_DOES_MARKDOWN=yes],
-            [MANDOC_DOES_MARKDOWN=no])
-      AC_MSG_RESULT([$MANDOC_DOES_MARKDOWN])
-      AC_SUBST([MANDOC_DOES_MARKDOWN])],
-      [AC_MSG_WARN([mandoc is missing, manuals can not be rebuilt]) ])
+      AM_CONDITIONAL([BUILD_MANUALS],
+                     ["$MANDOC" -T markdown </dev/null 2>/dev/null])
+      AM_COND_IF([BUILD_MANUALS],
+                 [AC_MSG_RESULT([yes])],
+                 [AC_MSG_RESULT([no])]) ])
+
+AM_COND_IF([BUILD_MANUALS], [],
+      [AC_MSG_WARN([col or usable mandoc is missing, manuals can not be rebuilt])])
 
 AC_CONFIG_FILES([Makefile src/Makefile doc/Makefile])
 AC_CONFIG_FILES([src/shell], [chmod +x src/shell])
diff --git a/doc/Makefile.am b/doc/Makefile.am
index 11a5a2f..7b151b4 100644
--- a/doc/Makefile.am
+++ b/doc/Makefile.am
@@ -3,17 +3,22 @@ dist_doc_DATA=	shell.md shell.txt
 EXTRA_DIST=	shell.mdoc
 DISTCLEANFILES=	shell.man shell.md shell.txt
 
+if !BUILD_MANUALS
+
+$(dist_man1_MANS) $(dist_doc_DATA):
+	@echo 'You lack the mandoc utility. Can not rebuild manuals' >&2
+	@exit 1
+
+else
+
 shell.man:	$(srcdir)/shell.mdoc
-	test -n "$(MANDOC)" && \
 	$(MANDOC) -T man -I os=Unix $(srcdir)/shell.mdoc >shell.man || true
 
 shell.md:	$(srcdir)/shell.mdoc
-	test -n "$(MANDOC)" && \
-	test "$(MANDOC_DOES_MARKDOWN)" = "yes" && \
 	$(MANDOC) -T markdown -I os=Unix $(srcdir)/shell.mdoc >shell.md || true
 
 shell.txt:	$(srcdir)/shell.mdoc
-	test -n "$(MANDOC)" && \
-	test -n "$(COL)" && \
 	$(MANDOC) -T ascii -I os=Unix $(srcdir)/shell.mdoc | \
 	$(COL) -b >shell.txt || true
+
+endif	# BUILD_MANUALS
diff --git a/doc/Makefile.in b/doc/Makefile.in
index 7ceabb6..3b4138c 100644
--- a/doc/Makefile.in
+++ b/doc/Makefile.in
@@ -174,7 +174,6 @@ LTLIBOBJS = @LTLIBOBJS@
 MAINT = @MAINT@
 MAKEINFO = @MAKEINFO@
 MANDOC = @MANDOC@
-MANDOC_DOES_MARKDOWN = @MANDOC_DOES_MARKDOWN@
 MKDIR_P = @MKDIR_P@
 MKTEMP = @MKTEMP@
 MKTEMP_TEMPLATE = @MKTEMP_TEMPLATE@
@@ -492,20 +491,19 @@ uninstall-man: uninstall-man1
 .PRECIOUS: Makefile
 
 
-shell.man:	$(srcdir)/shell.mdoc
-	test -n "$(MANDOC)" && \
-	$(MANDOC) -T man -I os=Unix $(srcdir)/shell.mdoc >shell.man || true
+@BUILD_MANUALS_FALSE@$(dist_man1_MANS) $(dist_doc_DATA):
+@BUILD_MANUALS_FALSE@	@echo 'You lack the mandoc utility. Can not rebuild manuals' >&2
+@BUILD_MANUALS_FALSE@	@exit 1
 
-shell.md:	$(srcdir)/shell.mdoc
-	test -n "$(MANDOC)" && \
-	test "$(MANDOC_DOES_MARKDOWN)" = "yes" && \
-	$(MANDOC) -T markdown -I os=Unix $(srcdir)/shell.mdoc >shell.md || true
+@BUILD_MANUALS_TRUE@shell.man:	$(srcdir)/shell.mdoc
+@BUILD_MANUALS_TRUE@	$(MANDOC) -T man -I os=Unix $(srcdir)/shell.mdoc >shell.man || true
 
-shell.txt:	$(srcdir)/shell.mdoc
-	test -n "$(MANDOC)" && \
-	test -n "$(COL)" && \
-	$(MANDOC) -T ascii -I os=Unix $(srcdir)/shell.mdoc | \
-	$(COL) -b >shell.txt || true
+@BUILD_MANUALS_TRUE@shell.md:	$(srcdir)/shell.mdoc
+@BUILD_MANUALS_TRUE@	$(MANDOC) -T markdown -I os=Unix $(srcdir)/shell.mdoc >shell.md || true
+
+@BUILD_MANUALS_TRUE@shell.txt:	$(srcdir)/shell.mdoc
+@BUILD_MANUALS_TRUE@	$(MANDOC) -T ascii -I os=Unix $(srcdir)/shell.mdoc | \
+@BUILD_MANUALS_TRUE@	$(COL) -b >shell.txt || true
 
 # Tell versions [3.59,3.63) of GNU make to not export all variables.
 # Otherwise a system limit (for SysV at least) may be exceeded.
diff --git a/doc/shell.man b/doc/shell.man
index 11763f9..f649762 100644
--- a/doc/shell.man
+++ b/doc/shell.man
@@ -1,5 +1,5 @@
 .\" Automatically generated from an mdoc input file.  Do not edit.
-.TH "SHELL" "1" "April 22, 2018" "Unix" "General Commands Manual"
+.TH "SHELL" "1" "July 19, 2018" "Unix" "General Commands Manual"
 .nh
 .if n .ad l
 .SH "NAME"
@@ -83,6 +83,7 @@ option.
 \fB\-f\fR
 Force the execution of the given command, even if it is not a valid
 login shell on the current system.
+The command needs to be specified with an absolute path.
 .TP 8n
 \fB\-k\fR
 Keep the temporary directory around after terminating the shell session.
@@ -106,6 +107,22 @@ Output version information and immediately terminate.
 \fBshell\fR
 uses the following environment variables:
 .TP 8n
+\fRSHELL\fR
+Used to determine what shell to start if a specific
+\fIshell\fR
+is not specified on the command line.
+If this variable is unset or empty, then
+\fB/bin/sh\fR
+will be used instead.
+.TP 8n
+\fRSHELL_SKEL\fR
+Directory to automatically pre-populate the temporary working directory with.
+This environment variable is not used if any of the
+\fB\-d\fR
+or
+\fB\-s\fR
+options are used on the command line.
+.TP 8n
 \fRTMPDIR\fR
 Directory in which to create the working directory when the
 \fB\-d\fR
@@ -115,11 +132,6 @@ This variable is used by
 which will revert to use
 \fI/tmp\fR
 if the variable is not set.
-.TP 8n
-\fRSHELL\fR
-Used to determine what shell to start if a specific
-\fIshell\fR
-is not specified on the command line.
 .PP
 \fBshell\fR
 clears the environment of the interactive shell that it starts, but
@@ -162,9 +174,9 @@ Start a new shell in a new temporary directory:
 .sp
 .RS 6n
 $ shell
-shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
+shell: info: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
 $ exit
-shell: INFO: Removing /tmp/shell-ksh.mJMHFTFE
+shell: info: Removing /tmp/shell-ksh.mJMHFTFE
 .RE
 .fi
 .PP
@@ -175,9 +187,9 @@ shell in a temporary directory:
 .sp
 .RS 6n
 $ shell dash
-shell: INFO: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
+shell: info: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
 $ exit
-shell: INFO: Removing /tmp/shell-dash.V7zU6EtZ
+shell: info: Removing /tmp/shell-dash.V7zU6EtZ
 .RE
 .fi
 .PP
@@ -188,10 +200,10 @@ shell in a specific directory:
 .sp
 .RS 6n
 $ shell -d "$HOME/testing" bash
-shell: INFO: Starting /usr/local/bin/bash in /home/myself/testing
+shell: info: Starting /usr/local/bin/bash in /home/myself/testing
 $ exit
 exit
-shell: INFO: Leaving /home/myself/testing in place
+shell: info: Leaving /home/myself/testing in place
 .RE
 .fi
 .PP
@@ -210,8 +222,8 @@ file copied from
 .sp
 .RS 6n
 $ shell -s "$HOME/skel" ksh -l
-shell: INFO: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
-shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
+shell: info: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
+shell: info: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
 $ ls -la
 total 36
 drwxr-xr-x   2 myself  wheel  512 Apr 15 12:55 .
@@ -224,7 +236,7 @@ drwxrwxrwt  28 root    wheel  512 Apr 21 14:15 ..
 -rw-r--r--   1 myself  wheel  215 Feb  9 10:18 .profile
 -rw-r--r--   1 myself  wheel  108 Apr 15 12:50 .vimrc
 $ exit
-shell: INFO: Removing /tmp/shell-ksh.ngEwbcpD
+shell: info: Removing /tmp/shell-ksh.ngEwbcpD
 .RE
 .fi
 .SH "SEE ALSO"
diff --git a/doc/shell.md b/doc/shell.md
index eb8920c..1bef967 100644
--- a/doc/shell.md
+++ b/doc/shell.md
@@ -80,6 +80,7 @@ The options are as follows:
 
 > Force the execution of the given command, even if it is not a valid
 > login shell on the current system.
+> The command needs to be specified with an absolute path.
 
 **-k**
 
@@ -109,6 +110,24 @@ The options are as follows:
 **shell**
 uses the following environment variables:
 
+`SHELL`
+
+> Used to determine what shell to start if a specific
+> *shell*
+> is not specified on the command line.
+> If this variable is unset or empty, then
+> **/bin/sh**
+> will be used instead.
+
+`SHELL_SKEL`
+
+> Directory to automatically pre-populate the temporary working directory with.
+> This environment variable is not used if any of the
+> **-d**
+> or
+> **-s**
+> options are used on the command line.
+
 `TMPDIR`
 
 > Directory in which to create the working directory when the
@@ -120,12 +139,6 @@ uses the following environment variables:
 > */tmp*
 > if the variable is not set.
 
-`SHELL`
-
-> Used to determine what shell to start if a specific
-> *shell*
-> is not specified on the command line.
-
 **shell**
 clears the environment of the interactive shell that it starts, but
 also sets the following environment variables:
@@ -174,28 +187,28 @@ also sets the following environment variables:
 Start a new shell in a new temporary directory:
 
 	$ shell
-	shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
+	shell: info: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
 	$ exit
-	shell: INFO: Removing /tmp/shell-ksh.mJMHFTFE
+	shell: info: Removing /tmp/shell-ksh.mJMHFTFE
 
 Start a new
 **dash**
 shell in a temporary directory:
 
 	$ shell dash
-	shell: INFO: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
+	shell: info: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
 	$ exit
-	shell: INFO: Removing /tmp/shell-dash.V7zU6EtZ
+	shell: info: Removing /tmp/shell-dash.V7zU6EtZ
 
 Start a new
 **bash**
 shell in a specific directory:
 
 	$ shell -d "$HOME/testing" bash
-	shell: INFO: Starting /usr/local/bin/bash in /home/myself/testing
+	shell: info: Starting /usr/local/bin/bash in /home/myself/testing
 	$ exit
 	exit
-	shell: INFO: Leaving /home/myself/testing in place
+	shell: info: Leaving /home/myself/testing in place
 
 Start
 **ksh**
@@ -210,8 +223,8 @@ file copied from
 *$HOME/skel*.
 
 	$ shell -s "$HOME/skel" ksh -l
-	shell: INFO: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
-	shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
+	shell: info: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
+	shell: info: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
 	$ ls -la
 	total 36
 	drwxr-xr-x   2 myself  wheel  512 Apr 15 12:55 .
@@ -224,7 +237,7 @@ file copied from
 	-rw-r--r--   1 myself  wheel  215 Feb  9 10:18 .profile
 	-rw-r--r--   1 myself  wheel  108 Apr 15 12:50 .vimrc
 	$ exit
-	shell: INFO: Removing /tmp/shell-ksh.ngEwbcpD
+	shell: info: Removing /tmp/shell-ksh.ngEwbcpD
 
 # SEE ALSO
 
@@ -248,4 +261,4 @@ The
 */etc/shells*
 file will still be used if it exists.
 
-Unix - April 22, 2018
+Unix - July 19, 2018
diff --git a/doc/shell.mdoc b/doc/shell.mdoc
index caf064e..a3b466c 100644
--- a/doc/shell.mdoc
+++ b/doc/shell.mdoc
@@ -74,6 +74,7 @@ option.
 .It Fl f
 Force the execution of the given command, even if it is not a valid
 login shell on the current system.
+The command needs to be specified with an absolute path.
 .It Fl k
 Keep the temporary directory around after terminating the shell session.
 .It Fl q
@@ -94,6 +95,20 @@ Output version information and immediately terminate.
 .Nm
 uses the following environment variables:
 .Bl -tag -width Ds
+.It Ev SHELL
+Used to determine what shell to start if a specific
+.Ar shell
+is not specified on the command line.
+If this variable is unset or empty, then
+.Cm /bin/sh
+will be used instead.
+.It Ev SHELL_SKEL
+Directory to automatically pre-populate the temporary working directory with.
+This environment variable is not used if any of the
+.Fl d
+or
+.Fl s
+options are used on the command line.
 .It Ev TMPDIR
 Directory in which to create the working directory when the
 .Fl d
@@ -103,10 +118,6 @@ This variable is used by
 which will revert to use
 .Pa /tmp
 if the variable is not set.
-.It Ev SHELL
-Used to determine what shell to start if a specific
-.Ar shell
-is not specified on the command line.
 .El
 .Pp
 .Nm
@@ -146,9 +157,9 @@ does not work.
 Start a new shell in a new temporary directory:
 .Bd -literal -offset Ds
 $ shell
-shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
+shell: info: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
 $ exit
-shell: INFO: Removing /tmp/shell-ksh.mJMHFTFE
+shell: info: Removing /tmp/shell-ksh.mJMHFTFE
 .Ed
 .Pp
 Start a new
@@ -156,9 +167,9 @@ Start a new
 shell in a temporary directory:
 .Bd -literal -offset Ds
 $ shell dash
-shell: INFO: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
+shell: info: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
 $ exit
-shell: INFO: Removing /tmp/shell-dash.V7zU6EtZ
+shell: info: Removing /tmp/shell-dash.V7zU6EtZ
 .Ed
 .Pp
 Start a new
@@ -166,10 +177,10 @@ Start a new
 shell in a specific directory:
 .Bd -literal -offset Ds
 $ shell -d "$HOME/testing" bash
-shell: INFO: Starting /usr/local/bin/bash in /home/myself/testing
+shell: info: Starting /usr/local/bin/bash in /home/myself/testing
 $ exit
 exit
-shell: INFO: Leaving /home/myself/testing in place
+shell: info: Leaving /home/myself/testing in place
 .Ed
 .Pp
 Start
@@ -185,8 +196,8 @@ file copied from
 .Pa $HOME/skel .
 .Bd -literal -offset Ds
 $ shell -s "$HOME/skel" ksh -l
-shell: INFO: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
-shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
+shell: info: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
+shell: info: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
 $ ls -la
 total 36
 drwxr-xr-x   2 myself  wheel  512 Apr 15 12:55 .
@@ -199,7 +210,7 @@ drwxrwxrwt  28 root    wheel  512 Apr 21 14:15 ..
 -rw-r--r--   1 myself  wheel  215 Feb  9 10:18 .profile
 -rw-r--r--   1 myself  wheel  108 Apr 15 12:50 .vimrc
 $ exit
-shell: INFO: Removing /tmp/shell-ksh.ngEwbcpD
+shell: info: Removing /tmp/shell-ksh.ngEwbcpD
 .Ed
 .Sh SEE ALSO
 .Xr mktemp 1
diff --git a/doc/shell.txt b/doc/shell.txt
index 2d7bc88..fd31125 100644
--- a/doc/shell.txt
+++ b/doc/shell.txt
@@ -41,7 +41,8 @@ DESCRIPTION
 	     conflicts with the -s option.
 
      -f	     Force the execution of the given command, even if it is not a
-	     valid login shell on the current system.
+	     valid login shell on the current system.  The command needs to be
+	     specified with an absolute path.
 
      -k	     Keep the temporary directory around after terminating the shell
 	     session.
@@ -59,13 +60,19 @@ DESCRIPTION
 ENVIRONMENT
      shell uses the following environment variables:
 
+     SHELL   Used to determine what shell to start if a specific shell is not
+	     specified on the command line.  If this variable is unset or
+	     empty, then /bin/sh will be used instead.
+
+     SHELL_SKEL
+	     Directory to automatically pre-populate the temporary working
+	     directory with.  This environment variable is not used if any of
+	     the -d or -s options are used on the command line.
+
      TMPDIR  Directory in which to create the working directory when the -d
 	     option is not used.  This variable is used by mktemp which will
 	     revert to use /tmp if the variable is not set.
 
-     SHELL   Used to determine what shell to start if a specific shell is not
-	     specified on the command line.
-
      shell clears the environment of the interactive shell that it starts, but
      also sets the following environment variables:
 
@@ -93,24 +100,24 @@ EXAMPLES
      Start a new shell in a new temporary directory:
 
 	   $ shell
-	   shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
+	   shell: info: Starting /bin/ksh in /tmp/shell-ksh.mJMHFTFE
 	   $ exit
-	   shell: INFO: Removing /tmp/shell-ksh.mJMHFTFE
+	   shell: info: Removing /tmp/shell-ksh.mJMHFTFE
 
      Start a new dash shell in a temporary directory:
 
 	   $ shell dash
-	   shell: INFO: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
+	   shell: info: Starting /usr/local/bin/dash in /tmp/shell-dash.V7zU6EtZ
 	   $ exit
-	   shell: INFO: Removing /tmp/shell-dash.V7zU6EtZ
+	   shell: info: Removing /tmp/shell-dash.V7zU6EtZ
 
      Start a new bash shell in a specific directory:
 
 	   $ shell -d "$HOME/testing" bash
-	   shell: INFO: Starting /usr/local/bin/bash in /home/myself/testing
+	   shell: info: Starting /usr/local/bin/bash in /home/myself/testing
 	   $ exit
 	   exit
-	   shell: INFO: Leaving /home/myself/testing in place
+	   shell: info: Leaving /home/myself/testing in place
 
      Start ksh as a login shell and pre-populate the temporary directory with
      the contents of $HOME/skel.  Note, starting the ksh shell as a login
@@ -118,8 +125,8 @@ EXAMPLES
      $HOME/skel.
 
 	   $ shell -s "$HOME/skel" ksh -l
-	   shell: INFO: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
-	   shell: INFO: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
+	   shell: info: Copying /home/myself/skel into /tmp/shell-ksh.ngEwbcpD
+	   shell: info: Starting /bin/ksh in /tmp/shell-ksh.ngEwbcpD
 	   $ ls -la
 	   total 36
 	   drwxr-xr-x	2 myself  wheel	 512 Apr 15 12:55 .
@@ -132,7 +139,7 @@ EXAMPLES
 	   -rw-r--r--	1 myself  wheel	 215 Feb  9 10:18 .profile
 	   -rw-r--r--	1 myself  wheel	 108 Apr 15 12:50 .vimrc
 	   $ exit
-	   shell: INFO: Removing /tmp/shell-ksh.ngEwbcpD
+	   shell: info: Removing /tmp/shell-ksh.ngEwbcpD
 
 SEE ALSO
      mktemp(1)
@@ -146,4 +153,4 @@ CAVEATS
      "getent shells" and may also lack the /etc/shells file.  The /etc/shells
      file will still be used if it exists.
 
-Unix				April 22, 2018				  Unix
+Unix				 July 19, 2018				  Unix
diff --git a/src/Makefile.in b/src/Makefile.in
index cb36513..96c9de4 100644
--- a/src/Makefile.in
+++ b/src/Makefile.in
@@ -170,7 +170,6 @@ LTLIBOBJS = @LTLIBOBJS@
 MAINT = @MAINT@
 MAKEINFO = @MAKEINFO@
 MANDOC = @MANDOC@
-MANDOC_DOES_MARKDOWN = @MANDOC_DOES_MARKDOWN@
 MKDIR_P = @MKDIR_P@
 MKTEMP = @MKTEMP@
 MKTEMP_TEMPLATE = @MKTEMP_TEMPLATE@
diff --git a/src/shell.in b/src/shell.in
index 3723c27..0a5af9b 100644
--- a/src/shell.in
+++ b/src/shell.in
@@ -23,17 +23,17 @@ perrorf ()
     # We mimic printf here, disable shellcheck warnings.
     # See https://unix.stackexchange.com/questions/438694
     # shellcheck disable=SC2059,SC2145
-    printf "$utility_name: ERROR: $@" >&2
+    printf "$utility_name: error: $@" >&2
 }
 
 pinfof ()
 {
-    # Same as above, but with 'INFO:' instead of 'ERROR:'.  Also
+    # Same as above, but with 'info:' instead of 'info:'.  Also
     # disables output if the global variable $quiet is 1.
 
     if [ "${quiet:-0}" -ne 1 ]; then
         # shellcheck disable=SC2059,SC2145
-        printf "$utility_name: INFO: $@" >&2
+        printf "$utility_name: info: $@" >&2
     fi
 }
 
@@ -138,7 +138,8 @@ while getopts 'd:fks:qv' opt; do
         k) keep=1       ;;
         q) quiet=1      ;;
         s) skel=$OPTARG ;;
-        v) output_version
+        v) quiet=0
+           output_version
            exit 0       ;;
         *) perrorf 'Unknown option on command line\n'
            exit 1
@@ -149,18 +150,15 @@ shift "$(( OPTIND - 1 ))"
 if [ -n "$tmpwd" ] && [ -n "$skel" ]; then
     perrorf 'Can not use both the -d and the -s option at the same time\n'
     exit 1
+elif [ -z "$tmpwd" ] && [ -z "$skel" ] && [ -n "$SHELL_SKEL" ]; then
+    skel=$SHELL_SKEL
 fi
 
 if [ -n "$1" ]; then
     shell="$1"
     shift
 else
-    shell="$SHELL"
-fi
-
-if [ -z "$shell" ]; then
-    perrorf 'Can not determine what shell to start\n'
-    exit 1
+    shell="${SHELL:-/bin/sh}"
 fi
 
 if [ "$force" -eq 0 ]; then