= SPSS System Variables =

'''System variables''' track the current state of the interpretter.

The dollar sign (`$`) is a disallowed leading character for user-defined variables because this is reserved for system variables.

<<TableOfContents>>

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== CaseNum ==

`$CASENUM` holds the current case's row number.

To create an 8-digit unique identifier number, try:

{{{
compute UniqueID = 10000000 + $casenum.
}}}

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== Date ==

`$DATE` holds the current date. Use `$TIME` instead of this.

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== Time ==

`$TIME` holds the current date and time as the number of seconds from October 14, 1582, to the execution time of a command accessing it.

This can be used to construct a timestamp.

{{{
data list free / a.
begin data.
1
end data.
dataset name TIMESTAMP.
execute.

string timestamp (A20).
compute #time = $time.

compute timestamp=concat(
  char.substr(string(xdate.year(#time),N4),3,2),
  string(xdate.month(#time),N2),
  string(xdate.mday(#time),N2),
  "_",
  string(xdate.hour(#time),N2),
  string(xdate.minute(#time),N2),
).
execute.

do if $casenum=1.
  write outfile 'timestamp.sps' /1 "define !timestamp() " timestamp " !enddefine.".
end if.
dataset close TIMESTAMP.
execute.

insert file='timestamp.sps'.
execute.
erase file='timestamp.sps'.
}}}

`!timestamp()` can now be used to reference the current date and time.



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