Add new "$_shell(CMD)" internal function

For testing a following patch, I wanted a way to send a SIGINT to GDB
from a breakpoint condition.  And I didn't want to do it from a Python
breakpoint or Python function, as I wanted to exercise non-Python code
paths.  So I thought I'd add a new $_shell internal function, that
runs a command under the shell, and returns the exit code.  With this,
I could write:

  (gdb) b foo if $_shell("kill -SIGINT $gdb_pid") != 0 || <other condition>

I think this is generally useful, hence I'm proposing it here.

Here's the new function in action:

 (gdb) p $_shell("true")
 $1 = 0
 (gdb) p $_shell("false")
 $2 = 1
 (gdb) p $_shell("echo hello")
 hello
 $3 = 0
 (gdb) p $_shell("foobar")
 bash: line 1: foobar: command not found
 $4 = 127
 (gdb) help function _shell
 $_shell - execute a shell command and returns the result.
 Usage: $_shell (command)
 Returns the command's exit code: zero on success, non-zero otherwise.
 (gdb)

NEWS and manual changes included.

Approved-By: Andrew Burgess <aburgess@redhat.com>
Approved-By: Tom Tromey <tom@tromey.com>
Approved-By: Eli Zaretskii <eliz@gnu.org>
Change-Id: I7e36d451ee6b428cbf41fded415ae2d6b4efaa4e

2 files changed, 37 insertions, 0 deletions

diff --git a/gdb/testsuite/gdb.base/default.exp b/gdb/testsuite/gdb.base/default.exp
index d0789a6..7e73db0 100644
--- a/gdb/testsuite/gdb.base/default.exp
+++ b/gdb/testsuite/gdb.base/default.exp
@@ -606,6 +606,7 @@ set show_conv_list \
 	{$_cimag = <internal function _cimag>} \
 	{$_creal = <internal function _creal>} \
 	{$_isvoid = <internal function _isvoid>} \
+	{$_shell = <internal function _shell>} \
 	{$_gdb_maint_setting_str = <internal function _gdb_maint_setting_str>} \
 	{$_gdb_maint_setting = <internal function _gdb_maint_setting>} \
 	{$_gdb_setting_str = <internal function _gdb_setting_str>} \
diff --git a/gdb/testsuite/gdb.base/shell.exp b/gdb/testsuite/gdb.base/shell.exp
index 31cdcb4..ba1691e 100644
--- a/gdb/testsuite/gdb.base/shell.exp
+++ b/gdb/testsuite/gdb.base/shell.exp
@@ -41,6 +41,42 @@ if { ! [ishost *-*-mingw*] } {
     gdb_test "p \$_shell_exitsignal" " = 2" "shell interrupt exitsignal"
 }
 
+# Test the $_shell convenience function.
+
+with_test_prefix "\$_shell convenience function" {
+    # Simple commands, check the result code.
+    gdb_test "p \$_shell(\"true\")" " = 0"
+    gdb_test "p \$_shell(\"false\")" " = 1"
+
+    # Test command with arguments.
+    gdb_test "p \$_shell(\"echo foo\")" "foo\r\n\\$${decimal} = 0"
+
+    # Check the type of the result.
+    gdb_test "ptype \$_shell(\"true\")" "type = int"
+
+    # Test passing a non-literal string as command name.
+    gdb_test "p \$cmd = \"echo bar\"" " = \"echo bar\""
+    gdb_test "p \$_shell(\$cmd)" "bar\r\n\\$${decimal} = 0"
+
+    # Test executing a non-existing command.  The result is
+    # shell-dependent, but most (all?) POSIX-like shells return 127 in
+    # this case.
+    gdb_test "p \$_shell(\"non-existing-command-foo-bar-qux\")" " = 127"
+
+    gdb_test "p \$_shell" \
+	" = <internal function _shell>"
+    gdb_test "ptype \$_shell" \
+	"type = <internal function>"
+
+    # Test error scenarios.
+    gdb_test "p \$_shell()" \
+	"You must provide one argument for \\\$_shell\\\."
+    gdb_test "p \$_shell(\"a\", \"b\")" \
+	"You must provide one argument for \\\$_shell\\\."
+    gdb_test "p \$_shell(1)" \
+	"Argument must be a string\\\."
+}
+
 # Define the user command "foo", used to test "pipe" command.
 gdb_test_multiple "define foo" "define foo" {
     -re "End with"  {