Awk array iteration for multi-dimensional arrays

Question

Awk offers associative indexing for array processing. Elements of 1 dimensional array can be iterated:

e.g.

for(index in arr1)
  print \"arr1[\" inde         


        

Answer 1

awk(1) was originally designed -- in part -- to be teaching tool for the C language, and multi-dimensional arrays have been in both C and awk(1) pretty much forever. as such POSIX IEEE 1003.2 standardized them.

To explore the syntax and semantics, if you create the following file called "test.awk":

BEGIN {
  KEY["a"]="a";
  KEY["b"]="b";
  KEY["c"]="c";
  MULTI["a"]["test_a"]="date a";
  MULTI["b"]["test_b"]="dbte b";
  MULTI["c"]["test_c"]="dcte c";
}
END {
  for(k in KEY) {
    kk="test_" k ;
    print MULTI[k][kk]
  }
  for(q in MULTI) {
    print q
  }
  for(p in MULTI) {
    for( pp in MULTI[p] ) {
      print MULTI[p][pp]
    }
  }
}

and run it with this command:

awk -f test.awk /dev/null

you will get the following output:

date a
dbte b
dcte c
a
b
c
date a
dbte b
dcte c

at least on Linux Mint 18 Cinnamon 64-bit 4.4.0-21-generic #37-Ubuntu SMP