diff options
| -rw-r--r-- | shell/hush.c | 44 |
1 files changed, 36 insertions, 8 deletions
diff --git a/shell/hush.c b/shell/hush.c index d5cea07a1..06e9af21a 100644 --- a/shell/hush.c +++ b/shell/hush.c @@ -2614,8 +2614,16 @@ static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg, char debug_printf_expand("%s\n", val); } else if (exp_op) { if (exp_op == '%' || exp_op == '#') { + /* Standard-mandated substring removal ops: + * ${parameter%word} - remove smallest suffix pattern + * ${parameter%%word} - remove largest suffix pattern + * ${parameter#word} - remove smallest prefix pattern + * ${parameter##word} - remove largest prefix pattern + * + * Word is expanded to produce a glob pattern. + * Then var's value is matched to it and matching part removed. + */ if (val) { - /* we need to do a pattern match */ bool match_at_left; char *loc; scan_t scan = pick_scan(exp_op, *exp_word, &match_at_left); @@ -2629,18 +2637,38 @@ static NOINLINE int expand_vars_to_list(o_string *output, int n, char *arg, char *loc = '\0'; } } else { /* one of :-=+? */ +//TODO: check validity of exp_op. Currently it can be anything. //TODO: handle ${VAR:N[:M]} here. N, M can be expressions similar to $((EXPR)): 2+2, 2+var etc - /* we need to do an expansion */ - int exp_test = (!val || ((exp_save == ':') && !val[0])); + /* Standard-mandated substitution ops: + * ${var?word} - indicate error if unset + * If var is unset, word (or a message indicating it is unset + * if word is null) is written to standard error + * and the shell exits with a non-zero exit status. + * Otherwise, the value of var is substituted. + * ${var-word} - use default value + * If var is unset, word is substituted. + * ${var=word} - assign and use default value + * If var is unset, word is assigned to var. + * In all cases, final value of var is substituted. + * ${var+word} - use alternative value + * If var is unset, null is substituted. + * Otherwise, word is substituted. + * + * Word is subjected to tilde expansion, parameter expansion, + * command substitution, and arithmetic expansion. + * If word is not needed, it is not expanded. + * + * Colon forms (${var:-word}, ${var:=word} etc) do the same, + * but also treat null var as if it is unset. + */ + int use_word = (!val || ((exp_save == ':') && !val[0])); if (exp_op == '+') - exp_test = !exp_test; + use_word = !use_word; debug_printf_expand("expand: op:%c (null:%s) test:%i\n", exp_op, - (exp_save == ':') ? "true" : "false", exp_test); - if (exp_test) { + (exp_save == ':') ? "true" : "false", use_word); + if (use_word) { if (exp_op == '?') { //TODO: how interactive bash aborts expansion mid-command? - /* ${var?[error_msg_if_unset]} */ - /* ${var:?[error_msg_if_unset_or_null]} */ /* mimic bash message */ die_if_script("%s: %s", var, |