hush: Add default value substitution support
Use standard sh syntax:
${VAR:-default}
Use default value: if VAR is set and non-null, expands to $VAR.
Otherwise, expands to default.
${VAR:=default}
Set default value: if VAR is set and non-null, expands to $VAR.
Otherwise, sets hush VAR to default and expands to default.
${VAR:+default}
If VAR is set and non-null, expands to the empty string.
Otherwise, expands to default.
Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>
diff --git a/common/hush.c b/common/hush.c
index 1eff182..39cf203 100644
--- a/common/hush.c
+++ b/common/hush.c
@@ -2743,13 +2743,50 @@
static char *lookup_param(char *src)
{
char *p;
+ char *sep;
+ char *default_val = NULL;
+ int assign = 0;
+ int expand_empty = 0;
if (!src)
return NULL;
- p = getenv(src);
- if (!p)
- p = get_local_var(src);
+ sep = strchr(src, ':');
+
+ if (sep) {
+ *sep = '\0';
+ if (*(sep + 1) == '-')
+ default_val = sep+2;
+ if (*(sep + 1) == '=') {
+ default_val = sep+2;
+ assign = 1;
+ }
+ if (*(sep + 1) == '+') {
+ default_val = sep+2;
+ expand_empty = 1;
+ }
+ }
+
+ p = getenv(src);
+ if (!p)
+ p = get_local_var(src);
+
+ if (!p || strlen(p) == 0) {
+ p = default_val;
+ if (assign) {
+ char *var = malloc(strlen(src)+strlen(default_val)+2);
+ if (var) {
+ sprintf(var, "%s=%s", src, default_val);
+ set_local_var(var, 0);
+ }
+ free(var);
+ }
+ } else if (expand_empty) {
+ p += strlen(p);
+ }
+
+ if (sep)
+ *sep = ':';
return p;
}