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Full Discussion: significance of statement
Top Forums UNIX for Dummies Questions & Answers significance of statement Post 302168712 by bakunin on Tuesday 19th of February 2008 08:07:10 AM
Old 02-19-2008
The script gets several parameters on the command line, the first one is "$1" inside the script, the second one "$2", etc. Here is an example for that mechanism:

Code:
user@machine:/~ # cat showparams.ksh

#! /usr/bin/ksh

print - "1st parameter: $1"
print - "2nd parameter: $2"
print - "3rd parameter: $3"
print - "4th parameter: $4"
exit 0

user@machine:/~ # ./showparams.ksh a b c d
1st parameter: a
2nd parameter: b
3rd parameter: c
4th parameter: d

By the way (this is not answering your question, but probably not wasted on a scripting beginner either): it is NOT good programming style to use these parameters as they are! Usually these parameters have some "meaning" in your script and it is better to define some variables, check the parameters if they make sense and then copy the commandline parameters to these variables and use them.

Here is an example. The script does nothing useful, just takes three parameters, an input file, an output file and a number and copies the content of the input file to the output file prepending every line with "Value was <number> ;". Its purpose is just to show hoe to first check and then subsequently use parameters passed on the command line.

Code:
#! /usr/bin/ksh

typeset    fInput="$1"            # file with the data to work on
typeset    fOutput="$2"           # file to store results to
typeset -i iSomeValue=0           # some numerical value

# before we use the parameters we test if they make sense:

                                  # make sure input is readable
if [ ! -r "$fInput" ] ; then      
     print -u2 "File $fInput is not readable or does not exist."
     exit 1
fi   

touch "$fOutput"                  # make sure output is writable
if [ $? -gt 0 ] ; then
     print -u2 "File $fOutput is not writeable."
     exit 1
fi
     
                                  # make sure $3 is really an integer
if [ -z "$(print - "$3" | sed 's/[0-9]//g')" ] ; then
     print -u2 "The third parameter must be integer, you entered $3"
     exit 1
else
     iSomeValue=$3
fi

# .... here goes the rest of your code ...

cat $fInput | while read chLine ; do
     print "Value was $iSomeValue ; $chLine" >> $fOutput
done

exit 0

To test this script create a file "inputfile", put some lines of text into it and call the script with

Code:
./script.ksh inputfile outputfile 25

which will work. Try

Code:
./script.ksh inputfile outputfile erroneous_value

then and it will fail with the error message:

The third parameter must be numeric, you entered erroneous_value.

I hope this helps.

bakunin
 

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LEARN ABOUT OSX

execute

EXECUTE(7)                                                         SQL Commands                                                         EXECUTE(7)

NAME

       EXECUTE - execute a prepared statement

SYNOPSIS

       EXECUTE name [ ( parameter [, ...] ) ]

DESCRIPTION

       EXECUTE  is  used  to execute a previously prepared statement. Since prepared statements only exist for the duration of a session, the pre-
       pared statement must have been created by a PREPARE statement executed earlier in the current session.

       If the PREPARE statement that created the statement specified some parameters, a compatible set of parameters must be passed to the EXECUTE
       statement,  or  else an error is raised. Note that (unlike functions) prepared statements are not overloaded based on the type or number of
       their parameters; the name of a prepared statement must be unique within a database session.

       For more information on the creation and usage of prepared statements, see PREPARE [prepare(7)].

PARAMETERS

       name   The name of the prepared statement to execute.

       parameter
              The actual value of a parameter to the prepared statement. This must be an expression yielding a value that is compatible  with  the
              data type of this parameter, as was determined when the prepared statement was created.

OUTPUTS

       The command tag returned by EXECUTE is that of the prepared statement, and not EXECUTE.

EXAMPLES

       Examples are given in the Examples [prepare(7)] section of the PREPARE [prepare(7)] documentation.

COMPATIBILITY

       The  SQL  standard includes an EXECUTE statement, but it is only for use in embedded SQL. This version of the EXECUTE statement also uses a
       somewhat different syntax.

SEE ALSO

       DEALLOCATE [deallocate(7)], PREPARE [prepare(7)]

SQL - Language Statements                                           2010-05-14                                                          EXECUTE(7)
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