hush: implement echo builtin

builtin_echo                                           -      36     +36
bltins                                               384     396     +12
------------------------------------------------------------------------------
(add/remove: 1/0 grow/shrink: 1/0 up/down: 48/0)               Total: 48 bytes

2 files changed, 16 insertions, 0 deletions

diff --git a/shell/Config.in b/shell/Config.in
index 0689b4ec2..312583e87 100644
--- a/shell/Config.in
+++ b/shell/Config.in
@@ -166,6 +166,7 @@ config HUSH
         select TRUE
         select FALSE
         select TEST
+        select ECHO
         help
           hush is a very small shell (just 18k) and it has fairly complete
           Bourne shell grammar.  It even handles all the normal flow control
diff --git a/shell/hush.c b/shell/hush.c
index 912cbb5d9..6bf4d1d19 100644
--- a/shell/hush.c
+++ b/shell/hush.c
@@ -614,6 +614,7 @@ static void free_strings(char **strings)
 
 /* Function prototypes for builtins */
 static int builtin_cd(char **argv);
+static int builtin_echo(char **argv);
 static int builtin_eval(char **argv);
 static int builtin_exec(char **argv);
 static int builtin_exit(char **argv);
@@ -652,6 +653,8 @@ struct built_in_command {
 #endif
 };
 
+/* For now, echo and test are unconditionally enabled.
+ * Maybe make it configurable? */
 static const struct built_in_command bltins[] = {
         BLTIN("["     , builtin_test, "Test condition"),
         BLTIN("[["    , builtin_test, "Test condition"),
@@ -661,6 +664,7 @@ static const struct built_in_command bltins[] = {
 //      BLTIN("break" , builtin_not_written, "Exit for, while or until loop"),
         BLTIN("cd"    , builtin_cd, "Change working directory"),
 //      BLTIN("continue", builtin_not_written, "Continue for, while or until loop"),
+        BLTIN("echo"  , builtin_echo, "Write strings to stdout"),
         BLTIN("eval"  , builtin_eval, "Construct and run shell command"),
         BLTIN("exec"  , builtin_exec, "Exec command, replacing this shell with the exec'd process"),
         BLTIN("exit"  , builtin_exit, "Exit from shell"),
@@ -841,6 +845,17 @@ static int builtin_test(char **argv)
         return test_main(argc, argv - argc);
 }
 
+/* built-in 'test' handler */
+static int builtin_echo(char **argv)
+{
+        int argc = 0;
+        while (*argv) {
+                argc++;
+                argv++;
+        }
+        return bb_echo(argc, argv - argc);
+}
+
 /* built-in 'eval' handler */
 static int builtin_eval(char **argv)
 {