sh: Allow aliases to force alias substitution on the following word.

If an alias's value ends with a space or tab, the next word is also
checked for aliases.

This is a POSIX feature. It is useful with utilities like command and
nohup (alias them to themselves followed by a space).

bin/sh/input.c

@@ -367,12 +367,16 @@ popstring(void)
 	struct strpush *sp = parsefile->strpush;
 
 	INTOFF;
+	if (sp->ap) {
+		if (parsenextc != sp->ap->val &&
+		    (parsenextc[-1] == ' ' || parsenextc[-1] == '\t'))
+			forcealias();
+		sp->ap->flag &= ~ALIASINUSE;
+	}
 	parsenextc = sp->prevstring;
 	parsenleft = sp->prevnleft;
 	parselleft = sp->prevlleft;
 /*out2fmt_flush("*** calling popstring: restoring to '%s'\n", parsenextc);*/
-	if (sp->ap)
-		sp->ap->flag &= ~ALIASINUSE;
 	parsefile->strpush = sp->prev;
 	if (sp != &(parsefile->basestrpush))
 		ckfree(sp);

bin/sh/parser.c

@@ -682,6 +682,12 @@ makebinary(int type, union node *n1, union node *n2)
 	return (n);
 }
 
+void
+forcealias(void)
+{
+	checkkwd |= CHKALIAS;
+}
+
 void
 fixredir(union node *n, const char *text, int err)
 {

bin/sh/parser.h

@@ -76,6 +76,7 @@ extern const char *const parsekwd[];
 
 
 union node *parsecmd(int);
+void forcealias(void);
 void fixredir(union node *, const char *, int);
 int goodname(const char *);
 int isassignment(const char *);

bin/sh/sh.1

@@ -32,7 +32,7 @@
 .\"	from: @(#)sh.1	8.6 (Berkeley) 5/4/95
 .\" $FreeBSD$
 .\"
-.Dd January 3, 2014
+.Dd January 26, 2014
 .Dt SH 1
 .Os
 .Sh NAME
@@ -533,6 +533,20 @@ would become
 .Pp
 .Dl "ls -F foobar"
 .Pp
+Aliases are also recognized after an alias
+whose value ends with a space or tab.
+For example, if there is also an alias called
+.Dq Li nohup
+with the value
+.Dq Li "nohup " ,
+then the input
+.Pp
+.Dl "nohup lf foobar"
+.Pp
+would become
+.Pp
+.Dl "nohup ls -F foobar"
+.Pp
 Aliases provide a convenient way for naive users to
 create shorthands for commands without having to learn how
 to create functions with arguments.

bin/sh/tests/parser/Makefile

@@ -18,6 +18,8 @@ FILES+=		alias10.0
 FILES+=		alias11.0
 FILES+=		alias12.0
 FILES+=		alias13.0
+FILES+=		alias14.0
+FILES+=		alias15.0 alias15.0.stdout
 FILES+=		and-pipe-not.0
 FILES+=		case1.0
 FILES+=		case2.0

bin/sh/tests/parser/alias14.0

@@ -0,0 +1,6 @@
+# $FreeBSD$
+
+alias command='command '
+alias alias0=exit
+eval 'command alias0 0'
+exit 3

bin/sh/tests/parser/alias15.0

@@ -0,0 +1,12 @@
+# $FreeBSD$
+
+f_echoanddo() {
+	printf '%s\n' "$*"
+	"$@"
+}
+
+alias echoanddo='f_echoanddo '
+alias alias0='echo test2'
+eval 'echoanddo echo test1'
+eval 'echoanddo alias0'
+exit 0

bin/sh/tests/parser/alias15.0.stdout

@@ -0,0 +1,4 @@
+echo test1
+test1
+echo test2
+test2