Function readoutput 

pub fn readoutput(in_fd: i32, qt: i32, readerror: &mut i32) -> Vec<String>

Port of Eprog parsecmd(char *cmd, char **eptr) from Src/exec.c:4878.

C body:

char *str;
Eprog prog;
for (str = cmd + 2; *str && *str != Outpar; str++);
if (!*str || cmd[1] != Inpar) {
    char *errstr = dupstrpfx(cmd, 2);
    untokenize(errstr);
    zerr("unterminated `%s...)'", errstr);
    return NULL;
}
*str = '\0';
if (eptr) *eptr = str+1;
if (!(prog = parse_string(cmd + 2, 0))) {
    zerr("parse error in process substitution");
    return NULL;
}
return prog;

Port of static LinkList readoutput(int in, int qt, int *readerror) from Src/exec.c:4805. Drain a command-substitution pipe fd and return the captured output split per qt.

qt=1 (quoted-substitution "$(...)"): single-element vec with the trailing-newline-trimmed buffer (empty buffer → Nularg sentinel per c:4861). qt=0 (unquoted $(...)): split on IFS via spacesplit; if GLOBSUBST is set, each word is shtokenized for downstream globbing.

readerror is set to the errno on read failure, 0 on clean EOF.