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Subject[PATCH 09/30] kconfig: add 'shell' built-in function
Date
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 v3: None
Changes in v2: None

scripts/kconfig/preprocess.c | 66 ++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 66 insertions(+)

diff --git a/scripts/kconfig/preprocess.c b/scripts/kconfig/preprocess.c
index e77cf7c..f4c606f 100644
--- a/scripts/kconfig/preprocess.c
+++ b/scripts/kconfig/preprocess.c
@@ -86,7 +86,73 @@ struct function {
char *(*func)(int argc, char *argv[]);
};

+/*
+ * Some commands treats commas verbatim. Concatenate arguments to get
+ * back the original input. The returned string must be freed when done.
+ */
+static char *join_args(int argc, char *argv[])
+{
+ size_t len = 0;
+ char *out;
+ int i;
+
+ for (i = 0; i < argc; i++)
+ len += strlen(argv[i]) + 1;
+
+ out = xmalloc(len);
+ out[0] = 0;
+ for (i = 0; i < argc; i++) {
+ strcat(out, argv[i]);
+ if (i != argc - 1)
+ strcat(out, ",");
+ }
+
+ return out;
+}
+
+static char *do_shell(int argc, char *argv[])
+{
+ FILE *p;
+ char buf[256];
+ char *cmd;
+ size_t nread;
+ int i;
+
+ cmd = join_args(argc, argv);
+
+ p = popen(cmd, "r");
+ if (!p) {
+ perror(cmd);
+ goto free;
+ }
+
+ 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);
+
+free:
+ free(cmd);
+
+ return xstrdup(buf);
+}
+
static const struct function function_table[] = {
+ { .name = "shell", .func = do_shell },
};

static char *function_call(const char *name, int argc, char *argv[])
--
2.7.4
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