how to iterate over two sets of data? - linux

Question

I'm trying to create my own program to do a recursive listing: each line corresponds to the full path of a single file. The tricky part I'm working on now is: I don't want bind mounts to trick my program into listing files twice.
So I already have a program that produces the right output except that if /foo is bind mounted to /bar then my program incorrectly lists
/foo/file
/bar/file
I need the program to list just what's below (EDIT: even if it was asked to list the contents of /foo)
/bar/file
One approach I thought of is to mount | grep bind | awk '{print $1 " " $3}' and then iterate over this to sed every line of the output, then sort -u.
My question is how do I iterate over the original output (a bunch of lines) and the output from mount (another bunch of lines)? (or is there a better approach) This needs to be POSIX (EDIT: and work with /bin/sh)

Answer 1

Place the 'mount | grep bind' command into the AWK within a BEGIN block and store the data.
Something like:
PROG | awk 'BEGIN{
# Define the data you want to store
# Assign to global arrays
command = "mount | grep bind";
while ((command | getline) > 0) {
count++;
mount[count] = $1;
mountPt[count] = $3
}
}
# Assuming input is line-by-line and that mountPt is the value
# that is undesired
{
replaceLine=0
for (i=1; i<=count; i++) {
idx = index($1, mountPt[i]);
if (idx == 1) {
replaceLine = 1;
break;
}
}
if (replaceLine == 1) {
sub(mountPt[i], mount[i], $1);
}
if (printed[$1] != 1) {
print $1;
}
printed[$1] = 1;
} '
Where I assume your current program, PROG, outputs to stdout.

Answer 2

find YourPath -print > YourFiles.txt
mount > Bind.txt
awk 'FNR == NR && $0 ~ /bind/ {
Bind[ $1] = $3
if( ( ThisLevel = split( $3, Unused, "/") - 1 ) > Level) Level = ThisLevel
}
FNR != NR && $0 !~ /^ *$/ {
RealName = $0
for( ThisLevel = Level; ThisLevel > 0; ThisLevel--){
match( $0, "(/[^/]*){" ThisLevel "}" )
UnBind = Bind[ substr( $0, 1, RLENGTH) ]
if( UnBind !~ /^$/) {
RealName = UnBind substr( $0, RLENGTH + 1)
ThisLevel = 0
}
}
if( ! File[ RealName]++) print RealName
}
' Bind.txt YourFiles.txt
search based on a exact path/bind comparaison from a bind array loaded first
Bind.txt and YourFiles.txt could be a direct redirection to be "1" instruction and no temporary files
have to be adapted (first part of awk) if path in bind are using space character (assume not here)
file path are changed live when reading, compare to an existing bind relation
print file if not yet known