ref: 3b65e3d6975fed9177cd827346e56f708c3ce6c1
dir: /rc/bin/E/
#!/bin/rc
# E file - B file, wait until it changes, exit
rfork e
if (! ~ $#* 1) {
echo usage: $0 file >[1=2]
exit usage
}
if (! test -e $1) {
echo $0: $1: no such file >[1=2]
exit no-file
}
otm = `{mtime $1 | awk '{print $1}'}
B $1
while (~ $otm `{mtime $1 | awk '{print $1}'})
sleep 1
exit ''