# awk 'BEGIN{system("date")|getline out;print out}'

Sun Jan  1 22:11:58 CST 2017

sh: 1: 0: not found

# awk 'BEGIN{"date"|getline out;print out}'

Sun Jan  1 22:13:47 CST 2017

# awk 'BEGIN{system("date")}'

Sun Jan  1 22:16:10 CST 2017

# awk 'BEGIN{system("ls")}'
ali.txt  a.log_bk  awk_file   b.txt  dir1     exe.shell  f1.txt_bk  f2.txt_bk  filename  func     learn_shell_bk    newfile  t      xarg.txt
a.log     a.txt       awk_files  dir    exe1.shell  f1.txt     f2.txt     f3.txt      fir.txt   learn_shell  learn_shell.save  sec.txt  text

# awk 'BEGIN{"ls"}'
# awk 'BEGIN{"ls" | getline out;print out}'
ali.txt