Add $Shell.execute()

4 files changed, 127 insertions, 6 deletions

diff --git a/docs/shell.md b/docs/shell.md
new file mode 100644
index 00000000..f453a1d0
--- /dev/null
+++ b/docs/shell.md
@@ -0,0 +1,117 @@
+# Shell Scripting
+
+Tomo comes with a built-in [lang](langs.md) called `Shell` for shell commands.
+This lets you write and invoke shell commands in a more type-safe way.
+
+```tomo
+user_name := ask("What's your name? ")
+_ := $Shell"echo Hello $user_name"
+```
+
+In the above example, there is no risk of code injection, because the
+user-controlled string is automatically escaped when performing interpolation.
+
+## Shell Methods
+
+### `by_line`
+
+**Description:**  
+Run a shell command and return an iterator over its output, line-by-line.
+
+**Signature:**  
+```tomo
+func by_line(command: Shell -> Void)
+```
+
+**Parameters:**
+
+- `command`: The command to run.
+
+**Returns:**  
+An optional iterator over the lines of the command's output. If the command fails
+to run, `none` will be returned.
+
+**Example:**  
+```tomo
+i := 1
+for line in $Shell"ping www.example.com":by_line()!:
+    stop if i > 5
+    i += 1
+```
+
+### `execute`
+
+**Description:**  
+Execute a shell command without capturing its output and return its exit status.
+
+**Signature:**  
+```tomo
+func execute(command: Shell -> Int32?)
+```
+
+**Parameters:**
+
+- `command`: The command to execute.
+
+**Returns:**  
+If the command exits normally, return its exit status. Otherwise return `none`.
+
+**Example:**  
+```tomo
+>> $Shell"touch file.txt":execute()
+= 0?
+```
+
+---
+
+### `run`
+
+**Description:**  
+Run a shell command and return the output text from `stdout`.
+
+**Signature:**  
+```tomo
+func run(command: Shell -> Text?)
+```
+
+**Parameters:**
+
+- `command`: The command to run.
+
+**Returns:**  
+If the program fails to run (e.g. a non-existent command), return `none`,
+otherwise return the entire standard output of the command as text. **Note:**
+if there is a trailing newline, it will be stripped.
+
+**Example:**  
+```tomo
+>> $Shell"seq 5":run()
+= "1$\n2$\n3$\n4$\n5"
+```
+
+---
+
+### `run_bytes`
+
+**Description:**  
+Run a shell command and return the output in raw bytes from `stdout`.
+
+**Signature:**  
+```tomo
+func run(command: Shell -> [Byte]?)
+```
+
+**Parameters:**
+
+- `command`: The command to run.
+
+**Returns:**  
+If the program fails to run (e.g. a non-existent command), return `none`,
+otherwise return the entire standard output of the command as an array of
+bytes.
+
+**Example:**  
+```tomo
+>> $Shell"seq 5":run_bytes()
+= [0x31, 0x0A, 0x32, 0x0A, 0x33, 0x0A, 0x34, 0x0A, 0x35, 0x0A]
+```
diff --git a/environment.c b/environment.c
index b785a8e3..2e1c4add 100644
--- a/environment.c
+++ b/environment.c
@@ -380,8 +380,8 @@ env_t *new_compilation_unit(CORD libname)
             {"escape_int", "Int$value_as_text", "func(i:Int -> Shell)"},
             {"escape_text", "Shell$escape_text", "func(text:Text -> Shell)"},
             {"escape_text_array", "Shell$escape_text_array", "func(texts:[Text] -> Shell)"},
-            {"execute", "Shell$execute", "func(command:Shell -> Int32)"},
-            {"run_bytes", "Shell$run", "func(command:Shell -> [Byte]?)"},
+            {"execute", "Shell$execute", "func(command:Shell -> Int32?)"},
+            {"run_bytes", "Shell$run_bytes", "func(command:Shell -> [Byte]?)"},
             {"run", "Shell$run", "func(command:Shell -> Text?)"},
         )},
         {"Text", TEXT_TYPE, "Text_t", "Text$info", TypedArray(ns_entry_t,
diff --git a/stdlib/shell.c b/stdlib/shell.c
index 08898acc..7c54950c 100644
--- a/stdlib/shell.c
+++ b/stdlib/shell.c
@@ -50,7 +50,7 @@ public OptionalArray_t Shell$run_bytes(Shell_t command)
         if (len + (size_t)just_read >= capacity)
             content = GC_REALLOC(content, (capacity *= 2));
 
-        memcpy(&content[len], chunk, (size_t)just_read);
+        memcpy(content + len, chunk, (size_t)just_read);
         len += (size_t)just_read;
     } while (just_read == sizeof(chunk));
 
@@ -75,10 +75,14 @@ public OptionalText_t Shell$run(Shell_t command)
     return Text$from_bytes(bytes);
 }
 
-public int32_t Shell$execute(Shell_t command)
+public OptionalInt32_t Shell$execute(Shell_t command)
 {
     const char *cmd_str = Text$as_c_string(command);
-    return system(cmd_str);
+    int status = system(cmd_str);
+    if (WIFEXITED(status))
+        return (OptionalInt32_t){.i=WEXITSTATUS(status)};
+    else
+        return (OptionalInt32_t){.is_none=true};
 }
 
 static void _line_reader_cleanup(FILE **f)
diff --git a/stdlib/shell.h b/stdlib/shell.h
index a8f35f65..500bb043 100644
--- a/stdlib/shell.h
+++ b/stdlib/shell.h
@@ -21,7 +21,7 @@ Shell_t Shell$escape_text(Text_t text);
 Shell_t Shell$escape_text_array(Array_t texts);
 OptionalArray_t Shell$run_bytes(Shell_t command);
 OptionalText_t Shell$run(Shell_t command);
-int32_t Shell$execute(Shell_t command);
+OptionalInt32_t Shell$execute(Shell_t command);
 
 #define Shell$hash Text$hash
 #define Shell$compare Text$compare