[PATCH v4 08/31] kconfig: add 'shell' built-in function

Masahiro Yamada
2018-05-17T06:18:51Z

This accepts a single command to execute. It returns the standard
output from it.

[Example code]

config HELLO
string
default "$(shell,echo hello world)"

config Y
def_bool $(shell,echo y)

[Result]

$ make -s alldefconfig && tail -n 2 .config
CONFIG_HELLO="hello world"
CONFIG_Y=y

Caveat:
Like environments, functions are expanded in the lexer. You cannot
pass symbols to function arguments. This is a limitation to simplify
the implementation. I want to avoid the dynamic function evaluation,
which would introduce much more complexity.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
---

Changes in v4:
- Accept only one argument to simplify the implementation

Changes in v3: None
Changes in v2: None

scripts/kconfig/preprocess.c | 41 +++++++++++++++++++++++++++++++++++++++++
1 file changed, 41 insertions(+)

diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c
index 5be28ec..d8c5f60 100644
--- a/scripts/kconfig/preprocess.c
+++ b/scripts/kconfig/preprocess.c
@@ -104,8 +104,49 @@ struct function {
char *(*func)(int argc, char *argv[], int old_argc, char *old_argv[]);
};

+static char *do_shell(int argc, char *argv[], int old_argc, char *old_argv[])
+{
+ FILE *p;
+ char buf[256];
+ char *cmd;
+ size_t nread;
+ int i;
+
+ cmd = argv[0];
+
+ p = popen(cmd, "r");
+ if (!p) {
+ perror(cmd);
+ exit(1);
+ }
+
+ nread = fread(buf, 1, sizeof(buf), p);
+ if (nread == sizeof(buf))
+ nread--;
+
+ /* remove trailing new lines */
+ while (buf[nread - 1] == '\n')
+ nread--;
+
+ buf[nread] = 0;
+
+ /* replace a new line with a space */
+ for (i = 0; i < nread; i++) {
+ if (buf[i] == '\n')
+ buf[i] = ' ';
+ }
+
+ if (pclose(p) == -1) {
+ perror(cmd);
+ exit(1);
+ }
+
+ return xstrdup(buf);
+}
+
static const struct function function_table[] = {
/* Name MIN MAX EXP? Function */
+ { "shell", 1, 1, true, do_shell },
};

#define FUNCTION_MAX_ARGS 16
--
2.7.4