Shell Programming and Scripting

What code works in native unix but not your script?

What is 'native unix' anyway?

Show your code. We cannot even guess what is happening when we can't see.

Sorry ... when I say "native unix" I mean typing in the commands directly without using a script and executing the script. By the way ... I got this working with the following:

linedate="12/14/2013"
linefmtdate=${linedate:6:4}${linedate:0:2}${linedate:3:2}

My problem now is how do I pad fields. For example if the date inputed is 4/23/2012, how do I turn this to 20120423?

Another way to do it would be:

Code:

VAR="12/14/2013"
IFS="/" read DD MM YYYY <<EOF
$VAR
EOF

NEWVAR=$(sprintf "%04d%02d%02d" $YYYY $MM $DD)

I'm still not getting this ... I'm not sure what IFS is .. The last set of instructions works, but what I really want is:

Read in data
field1 is everything up to first /
field2 is everything up to second /
field3 is everything up to third /
new data is field3field1field2 where field 1 and 2 are padded with 0 to make 2 digits

ie 12/24/2013 would be 20131224
2/10/2012 would be 20120210
1/1/2000 would be 20000101

Is there a simple way to do this?

---------- Post updated at 03:23 PM ---------- Previous update was at 03:22 PM ----------

also .. can any of you recommend a basic unix script programming book?

I gave you exactly what you asked for, in pretty much the exact way you wanted it.

IFS is a special variable which controls what the shell splits upon. It's usually space, but you can tell it to split on any character or characters.

So we tell read to split upon / while reading into three different variables -- YYYY, MM, and DD. We feed it that text using a here-document, which acts like file redirection but is right inside the shell. If you wanted to read directly from the keyboard, you can chop of everything from <<EOF to EOF and it will read direct instead of from a variable.

Then we use another shell builtin, printf, to zero-pad the numbers the way you want. It takes a format string, then one or more values after that to fill out the format string.

%d means "integer".
"%04d" means "integer, padded with zeroes up to four digits".

Try typing this into your shell and you'll see what it does:

Code:

printf "%08d\n" 5

So %04d is for the year, and %02d are for the months and days.

And we capture its output in $( ) brackets to turn it into a string variable.

The advanced bash scripting guide is a good reference, particularly the reference cards.

Think I finally got it

Code in shell script

Code:

linedate="2/14/2013"
IFS="/" read mm dd yyyy <<EOF
$linedate
EOF
newvar=$(printf "%04d%02d%02d" $yyyy $mm $dd)
echo $newvar $linedate

Output from echo

Code:

20130214 2/14/2013

Pretty sure it was a case of me not understanding what I was doing ... but it works now. Thank you again for all your help.