What's going on in this function?

It would help if you note that you're using ksh or zsh - they both have a print shell built-in.

  1. A=$1
  2. print "`date '+%m/%d/%y  %H:%M:%S'`: $A"  >> LOGFILE.txt
  3. print "$A"

Line 1: $1 means "first argument to function log()". So, assign value of first argument to log to variable named "A".

Line 2: The "grave accents" (a.k.a. "back tics") mean "run the enclosed command and substite its output for the back-tic'ed string. $A means "the value of variable named "A"". So, compose a string by running date, and interpolate the value of A. Shells typically distinguish between rvalue (name assigned to) and lvalue (contents of variable. The ">>" means put it on the end of a file named "LOGFILE".

Line 3: Just write value of variable named "A" to stdout.

The log function is a pretty common way of doing sh-script logging: write one copy of any message to a file with a date stamp, write one copy to stdout. The sh-script runs in a terminal window, and messages just scroll by, but also appear in a file for later debugging.

You invocation of log in the true-clause of the if-statement passes the entire string "not a zero value" as the first formal argument of function log. That's what value gets assigned to variable "A" in line 1.

A=$1

assigns the first function argument to the variable A

print "`date '+%m/%d/%y  %H:%M:%S'`: $A"  >> LOGFILE.txt

prints the date and the value of variable A and appends it to LOGFILE.txt

print "$A"

prints the first function argument

BTW, in the line: if ["blah" != "0"]

There should be space after [ and before ], like this:

if [ "blah" != "0" ]

BTW, the print is not a standard command in some shells.