Awk

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References

Awk Program Examples

ps al | awk '{print $2}'                                         # Print second field of ps output
arp -n 10.137.3.129|awk '/ether/{print $3}'                      # Print third field of arp output, if line contains 'ether' somewhere
getent hosts unix.stackexchange.com | awk '{ print $1 ; exit }'  # Print only first line, then exit
find /proc -type l | awk -F"/" '{print $3}'                      # Print second folder name (i.e. process pid)

Example of parsing an XML file (and comparing with perl):

cat FILE
#        <configuration buildProperties="" description="" id="some_id.1525790178" name="some_name" parent="some_parent">
cat FILE | awk -F "[= <>\"]+" '/<configuration / { if ($8 == "some_name") print $6 }'
# some_id.1525790178
cat FILE | perl -lne 'print $1 if /<configuration .* id="([^"]*)" name="some_name"/'
# some_id.1525790178

Tips

  • Defining environment variable - Using an Awk script and Bash builtin eval
eval $(awk 'BEGIN{printf "MY_VAR=value";}')
echo $MY_VAR
  • Hexadecimal conversion - Use strtonum to convert parameter:
{
    print strtonum($1);       # decimal, octal or hexa (guessed from prefix)
    print strtonum("0"$2);    # To force octal
    print strtonum("0x"$3);   # To force hexadecimal
}
  • Using environment variables - Use ENvIRON["NAME"]:
{ print strtonum("0x"ENVIRON["STARTADDR"]); }
  • Pass command-line parameters - Awk variables can be defined directly on the invocation line:
awk -v myvar=123 'BEGIN { printf "myvar is %d\n",myvar }'     # Use -v (before program text) for var used in BEGIN section
echo foo | awk '{ printf "myvar is %d\n",myvar }' myvar=123   # Otherwise specify var after program text
  • Pass command-line parameters - Awk defines the variables ARGC and ARGV:
awk BEGIN {
  for (i = 0; i < ARGC; i++)
  print ARGV[i]
} inventory-shipped BBS-list