.TH validate "" "" "/rdb Command"
.PC "Find invalid data"
\fBvalidate  '\fIpattern \fB{ \fIaction \fB} ...' < \fItableorlist\fR
.PP
.II "table^validate"
.II "data^validate"
The command
.B validate
checks your tables and a list of invalid data.
It also prints messages of your choosing, and shows
you the line that caused the error.
It is almost identical to a combination of the commands
.B row
and
.BR compute .
.PP
.B validate
passes your commands to
.B awk
after it has converted your column names to
.BR $1 ,
.BR $2 ,
and so on, which is how
.B awk
refers to columns.
.PP
.I pattern
is a logical condition that indicates invalidity in the data;
for example, it may give values that are negative and should not be,
or greater than they should be.
.I action
is what to do about it;
usually, this is to print a message.
.SH Example
The first example is simple.
Once again, consider table
.BR inventory ,
which is as follows:
.DM
Item#   Onhand  Cost    Value   Description   
-----   ------  ----    -----   --------------
    1        3    50      150   rubber gloves 
    2      100     X      500   test tubes    
    3       -5    80     -400   clamps        
    4       23    19      437   plates        
    5      -99    24    -2376   cleaning cloth
    6       89   147    13083   bunsen burners
    7        5   175      875   scales        
.DE
.PP
Several invalid values have crept into this table.
You might wish to check that no item in column
.B Onhand
is less than zero.
To do so, type the command:
.DM
validate 'Onhand < 0 {print "negative Onhand in line " NR}' < badinventory
.DE
.PP
This prints the following on the standard output:
.DM
Item#   Onhand  Cost    Value   Description   
-----   ------  ----    -----   --------------
    1        3    50      150   rubber gloves 
    2      100     X      500   test tubes    
negative Onhand in line 3
    3       -5    80     -400   clamps        
    4       23    19      437   plates        
negative Onhand in line 5
    5      -99    24    -2376   cleaning cloth
    6       89   147    13083   bunsen burners
    7        5   175      875   scales        
.DE
.PP
The variable
.B NR
means number of record or row.
This variable is built into
.BR awk ,
which
replaces it with the number of the line it is processing.
.PP
The next example is complex.
Note that if you wish, you can write a command line for
.B validate
into a file, to create a customized validation command.
You can put many tests and messages in one validation file.
For example, the following command file, called
.BR validateinv ,
thoroughly checks table inventory:
.DM
echo validating badinventory
.sp \n(pDu
validate '{if (Onhand < 0 ) print "negative Onhand in line " NR; \e
        if (Value < 0 ) print "negative Value in line " NR; \e
        if (Cost ~ /[A-Za-z]/) print "letter in Cost in line " NR; }' \e
        < badinventory
.DE
.PP
To validate table
.BR inventory ,
just type:
.DM
	validating badinventory
.DE
.PP
This prints the following on the standard output:
.DM
Item#   Onhand  Cost    Value   Description   
-----   ------  ----    -----   --------------
    1        3    50      150   rubber gloves 
letter in Cost in line 2
    2      100     X      500   test tubes    
negative Onhand in line 3
negative Value in line 3
    3       -5    80     -400   clamps        
    4       23    19      437   plates        
negative Onhand in line 5
negative Value in line 5
    5      -99    24    -2376   cleaning cloth
    6       89   147    13083   bunsen burners
    7        5   175      875   scales        
.DE
.PP
You may wish to redirect the output of
.B validate
to a file, bring it into your editor, and
correct the errors and remove the error lines as you go.
To make it easier to find those error lines in
the editor, you could have all error lines contain a string
that is easy to find, such as
.BR ERROR .
.PP
If you only want to see the error lines, use the command
.BR row .
.SH "See Also"
.SH "Logical Conditions"
.B
compute,
row
.R
.br
COHERENT Tutorials:
.B
Introduction to the awk Language
.R