UnixTips.net

#!/bin/bash

if [ $# -ne 1 ]
then
echo "Usage: $0 "
exit 0
fi

host=$1

If no hostname is specified output will be:

./1.myscript.bash 
Usage: ./1.myscript.bash  

I tested this on LINUX

Use as you please.

# date
Mon May 18 16:16:29 EDT 2015
# date '+%s' -d "now"
1431980193
# date '+%s' -d "May 18 2014"
1400385600
# echo $(( (1431980193 - 1400385600) / 86400 )) 
365

Handy gsub examples:

Removing the trailing % in the 5th field.

# echo "1 2 3 4 85%" | awk '/%/{gsub( /%/," ",$5); print}'
1 2 3 4 85

• /%/ operate only on lines with a %
  (this means empty lines are skipped)
• gsub(a,b,c) match the regular expression a, replace it with b,
  and do all this with the contents of c
• print print the contents of the entire line

# echo "1 2 3 4 85%" | awk '/%/{gsub( /%/," ",$5); print $5}'
85

• /%/ operate only on lines with a %
  (this means empty lines are skipped)
• gsub(a,b,c) match the regular expression a, replace it with b,
  and do all this with the contents of c
• print $5 print the contents of the 5th field

# echo "1 2 3 4 85%" | awk '/%/{gsub( /%/," ",$5); print $5","$2}'
85 ,2

• /%/ operate only on lines with a %
  (this means empty lines are skipped)
• gsub(a,b,c) match the regular expression a, replace it with b,
  and do all this with the contents of c
• print $5″,”$2 print the contents of field 5, a comma, then field 2

# echo "1:2:3:4:85%" |  awk -F: '/%/{gsub( /%/," ",$5); print$5","$2}'
85 ,2

• -F: use : as field separator
• /%/ operate only on lines with a %
  (this means empty lines are skipped)
• gsub(a,b,c) match the regular expression a, replace it with b,
  and do all this with the contents of c
• print$5″,”$2 print the contents of field 5, a comma, then field 2

Need to remove white spaces?

# echo "1: 2 :3:4:5:6" | awk -F: '{print $2}'
 2 

# echo "1: 2 :3:4:5:6" | awk 'BEGIN{FS=OFS=":"}{gsub(/^[ \t]+/,"",$2);gsub(/[ \t]+$/,"",$2)}1'
1:2:3:4:5:6

• BEGIN{FS=OFS=”:”} – use : as field separator
• gsub(/^[ \t]+/,””,$2); – starting at the beginning (^) replace all (+ = zero or more, greedy)
  consecutive tabs and spaces with an empty string
• gsub(/[ \t]+$/,””,$2)} – do the same, but now for all space up to the end of string ($)
  1 – =”true”. Shorthand for “use default action”, which is print $0
  – that is, print the entire (modified) line

# echo "1: 2 :3:4:5:6" | awk 'BEGIN{FS=OFS=":"}{gsub(/^[ \t]+/,"",$2);gsub(/[ \t]+$/,"",$2); print $2}'
2

Same as above but print specific fields.

• ;print $2 print the 2nd field. Notice the print is before the curly bracket } and followed by a semi-colon :

This post was based on the following stockoverflow.com question:
http://stackoverflow.com/questions/20600982/remove-leading-and-trailing-space-in-field-in-awk