Fix various typos / Update README.md

README.md:
- Add a table of contents.
- Start a list of system-specific instructions for installing build
  dependencies in README.md, initially for Android/Termux and
  macOS. Runtime dependencies are also mentioned where applicable
  (yes, there are system that ship without tput(1) and getconf(1)).

Other files:
- Fix various typos.

README.md

@@ -19,15 +19,47 @@ and click on commit messages for full details.
 For all fixes, see [the commit log](https://github.com/ksh93/ksh/commits/1.0).
 For known issues in the current release, see [TODO](https://github.com/ksh93/ksh/blob/1.0/TODO).
 
-## Build
+## Table of contents ##
+
+* [Installing from source](#user-content-installing-from-source)
+    * [Prepare](#user-content-prepare)
+    * [Build](#user-content-build)
+    * [Test](#user-content-test)
+    * [Install](#user-content-install)
+* [What is ksh93?](#user-content-what-is-ksh93)
+
+## Installing from source
+
+You can download a [release](releases) tarball,
+or clone the current code from the 1.0 branch:
+`git clone -b 1.0 https://github.com/ksh93/ksh`
+
+### Prepare
+
+The build system requires only a basic POSIX-compatible shell, utilities and
+compiler environment. The `cc`, `ar` and `getconf` commands are needed at
+build time. The `tput` and `getconf` commands are used at runtime if
+available (for multiline editing and to complete the `getconf` built-in,
+respectively). Not all systems come with all of these preinstalled. Here are
+system-specific instructions for making them available:
+
+* **Android/[Termux](https://termux.dev/):**
+  install dependencies using `pkg install`.
+    * Build dependencies: `clang`, `binutils`, `getconf`
+    * Runtime dependencies (optional): `ncurses-utils`, `getconf`
+* **macOS:**
+  install the Xcode Command Line Tools:    
+  `xcode-select --install`
+
+### Build
 
 To build ksh with a custom configuration of features, edit
 [`src/cmd/ksh93/SHOPT.sh`](https://github.com/ksh93/ksh/blob/1.0/src/cmd/ksh93/SHOPT.sh).
 
 On systems such as NetBSD and OpenBSD, where `/bin/ksh` is not ksh93 and the
 preinstalled `/etc/ksh.kshrc` profile script is incompatible with ksh93, you'll
 want to disable `SHOPT_SYSRC` to avoid loading it on startup -- unless you can
-edit it to make it compatible with ksh93. This geneerally involves differences
+edit it to make it compatible with ksh93. This generally involves differences
 in the declaration and usage of local variables in functions.
 
 Then `cd` to the top directory and run:
@@ -37,6 +69,7 @@ bin/package make
 ```
 
 To suppress compiler output, use `quiet make` instead of `make`.
+
 In some non-POSIX shells you might need to prepend `sh` to all calls to `bin/package`.
 
 Parallel building is supported by appending `-j` followed by the

src/cmd/INIT/README-mamake.md

@@ -136,7 +136,7 @@ written as a separate line to its standard input. The value of the expansion
 is the output of *s* with each newline changed back into a space, except
 that a terminating newline (if any) is discarded.
 This mechanism allows easy editing of variable values containing multiple
-pathnames using line-oriented utilities thet read from standard input,
+pathnames using line-oriented utilities that read from standard input,
 such as `sed`(1) or `grep`(1).
 For example, if the automatic variable `%{^}` (see below) contains `foo.c
 bar.c baz.c`, then `%{^|sed 's/\.c$//'}` yields `foo bar baz`.
@@ -169,7 +169,7 @@ previously processed or referenced prerequisites.
 
 `%{?}` is a space-separate list of the current rule's previously processed
 prerequisites that have been updated by a shell action (see `exec` below)
-during the current `mamake` run. Prequisites that were already up to date,
+during the current `mamake` run. Prerequisites that were already up to date,
 or prerequisites that do not contain a shell action, are not included.
 
 ## Commands ##
@@ -340,7 +340,7 @@ of the line in the rule.
 After MAM variable expansion, *viewpathing* is applied.
 The first colon-separated element of `%{VPATH}` is considered
 the object code directory and the second the source code directory;
-viewpathing provides the first with a vew to the second.
+viewpathing provides the first with a view to the second.
 Viewpathing applies two transformations.
 
 The first is *prerequisite replacement*.
@@ -375,7 +375,7 @@ in the following format is written to standard error:
 
     # path/to/Mamfile: startline-endline: rule
 
-During script execution, shell action comands are traced using the
+During script execution, shell action commands are traced using the
 shell's xtrace option, unless the rule has the `notrace` attribute.
 
 #### Strict level 2+ change ####

src/cmd/INIT/mamake.c

@@ -1663,7 +1663,7 @@ static void run(Rule_t *r, char *s)
 		if (x && state.shim)
 		{
 			/* Also subject the user-set shim to viewpathing
-			 * (plus other code preprended above, but it should not contain anything viewpathable) */
+			 * (plus other code prepended above, but it should not contain anything viewpathable) */
 			char	*pre = use(buf);
 			size_t	n = strlen(pre);
 			if (!(tofree = malloc(n + strlen(s) + 1)))
@@ -2233,7 +2233,7 @@ static void make(Rule_t *r, Makestate_t *parentstate)
 			{
 				/* loop block done */
 				if (*t)
-					error_out("superflous arguments", u);
+					error_out("syntax error", u);
 				break;
 			}
 			/* make block done */

src/cmd/ksh93/features/externs

@@ -188,7 +188,7 @@ tst	note{ determining size of PID variables }end output{
 	exit 1
 }end
 
-# execve(3) breakage on Android/Termux (as of API 35)
+# execve(3) breakage on Android/Termux (early versions of API 35)
 tst	execve_ignores_argv0 note{ does execve(3) ignore the specified argv[0] }end output{
 	#include <string.h>
 	#include <unistd.h>
@@ -201,7 +201,7 @@ tst	execve_ignores_argv0 note{ does execve(3) ignore the specified argv[0] }end
 		sprintf(b,"_KSH_EXECVE_TEST_%d=y",(int)getpid());
 		newenv[0] = b;
 		newenv[1] = NULL;
-		/* check if we've alreay been re-exec'ed */
+		/* check if we've already been re-exec'ed */
 		for (i = 0; environ[i]; i++)
 			if (strcmp(environ[i],newenv[0])==0)
 				return !(strcmp(argv[0],"TEST_OK")!=0);

src/cmd/ksh93/kshrc.sh

@@ -37,7 +37,7 @@ typeset .rc
 .rc.tty=${.rc.tty#/dev/}
 
 if	[[ -v INSTALLROOT ]]
-then	# do not intefere with the regular ksh history
+then	# do not interfere with the regular ksh history
 	[[ -d $INSTALLROOT/var ]] || mkdir -p "$INSTALLROOT/var"
 	HISTFILE=$INSTALLROOT/var/sh_history_${.rc.tty//\//_}
 fi

src/cmd/ksh93/sh/parse.c

@@ -252,7 +252,7 @@ static void check_typedef(struct comnod *tp, char intypeset)
  * Hack to avoid an inconsistent state if a 'typeset -T' or 'enum' declaration is parsed but not executed:
  *
  * The parser needs to know about to-be-created type built-ins before their declarations are executed,
- * otherwise assignment-arguments with parenteses -- e.g., Type_t foo=(bar baz) -- are a syntax error if
+ * otherwise assignment-arguments with parentheses -- e.g., Type_t foo=(bar baz) -- are a syntax error if
  * parsed within the same pass as the 'typeset -T Type_t=(...)' declaration. This would be especially bad
  * in dot scripts, which are completely parsed in one single sh_parse() call before execution.
  *

src/lib/libast/Mamfile

@@ -81,7 +81,7 @@ make install virtual
 	note *
 
 	note * The standards test influences all subsequent iffe feature tests, so must be made first
-	note * Block parallellisation here by nesting FEATURE/standards in ast_standards.h
+	note * Block parallelisation here by nesting FEATURE/standards in ast_standards.h
 	make ast_standards.h
 		make FEATURE/standards
 			makp features/standards