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/* execve.c: an execve() for geriatric unices without #! */
/*
NOTE: this file depends on a hack in footobar.c which places two free
spots before av[][] so that execve does not have to call malloc.
*/
#include "rc.h"
#include <errno.h>
#define giveupif(x) { if (x) goto fail; }
extern int rc_execve(char *path, char **av, char **ev) {
int fd, len, fst, snd, end;
bool noarg;
char pb[256]; /* arbitrary but generous limit */
execve(path, av, ev);
if (errno != ENOEXEC)
return -1;
fd = rc_open(path, rFrom);
giveupif(fd < 0);
len = read(fd, pb, sizeof pb);
close(fd);
/* reject scripts which don't begin with #! */
giveupif(len <= 0 || pb[0] != '#' || pb[1] != '!');
for (fst = 2; fst < len && (pb[fst] == ' ' || pb[fst] == '\t'); fst++)
; /* skip leading whitespace */
giveupif(fst == len);
for (snd = fst; snd < len && pb[snd] != ' ' && pb[snd] != '\t' && pb[snd] != '\n'; snd++)
; /* skip first arg */
giveupif(snd == len);
noarg = (pb[snd] == '\n');
pb[snd++] = '\0'; /* null terminate the first arg */
if (!noarg) {
while (snd < len && (pb[snd] == ' ' || pb[snd] == '\t'))
snd++; /* skip whitespace to second arg */
giveupif(snd == len);
noarg = (pb[snd] == '\n'); /* could have trailing whitespace after only one arg */
if (!noarg) {
for (end = snd; end < len && pb[end] != ' ' && pb[end] != '\t' && pb[end] != '\n'; end++)
; /* skip to the end of the second arg */
giveupif(end == len);
if (pb[end] == '\n') {
pb[end] = '\0'; /* null terminate the first arg */
} else { /* else check for a spurious third arg */
pb[end++] = '\0';
while (end < len && (pb[end] == ' ' || pb[end] == '\t'))
end++;
giveupif(end == len || pb[end] != '\n');
}
}
}
*av = path;
if (!noarg)
*--av = pb + snd;
*--av = pb + fst;
execve(*av, av, ev);
return -1;
fail: errno = ENOEXEC;
return -1;
}
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