Awk: Difference between revisions

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* '''Pass command-line parameters''' - Awk variables can be defined directly on the invocation line:
* '''Pass command-line parameters''' - Awk variables can be defined directly on the invocation line:
<source lang="awk">
<source lang="awk">
awk '{ printf "myvar is %d\",myvar ; }' myvar=123
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
</source>
</source>

Revision as of 14:16, 16 March 2016

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)

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