Shell Programming and Scripting

$ echo "one two three" | awk '{
  gsub(/wo/,"_BEG_&_END_",$2); 
  print }'
one t_BEG_wo_END_ three 
$ echo "one two three" | awk '{
  tmp="foo"; 
  gsub(/wo/,"_BEG_" tmp "_END_",$2); 
  print}'
one t_BEG_foo_END_ three
$ echo "one two three" | awk '{
  tmp["wo"]="foo"; 
  gsub(/wo/,"_BEG_" tmp["wo"] "_END_",$2); 
  print}'
one t_BEG_foo_END_ three
$ echo "one two three" | awk '{
  tmp["wo"]="foo"; 
  a="wo"; 
  gsub(/wo/,"_BEG_" tmp[a] "_END_",$2); 
  print}'
one t_BEG_foo_END_ three

$ echo "one two three" | awk '{tmp["wo"]="foo"; gsub(/wo/,"_BEG_" tmp["&"] "_END_",$2); print}'
one t_BEG__END_ three

$ echo "one two three" | awk '{tmp["wo"]="foo";
if(match($0, "wo")) {
    fnd=substr($0, RSTART, RLENGTH);
    print substr($0, 1, RSTART-1) "_BEG_" tmp[fnd] "_END_" substr($0,RSTART+RLENGTH)
}}'
one t_BEG_foo_END_ three

gsub(/pattern/,array[var],$0);

gsub(/pattern/,array["&"],$0);

awk 'function arrayrep(pattern, array, string) {
    while (match(string, pattern)) {
        fnd=substr(string, RSTART, RLENGTH);
        string = substr(string, 1, RSTART-1) array[fnd] substr(string,RSTART+RLENGTH)}
    return string
}
BEGIN {
  G["%NAME1%"]="Jack"
  G["%NAME2%"]="Jill"
  print arrayrep("%[^%]*%", G, "%NAME1% and %NAME2% went up the hill ... %NAME1% fell down") }'