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Full Discussion: Very simple question
Top Forums Shell Programming and Scripting Very simple question Post 302804941 by franksunnn on Thursday 9th of May 2013 11:08:53 AM
Old 05-09-2013
Question Very simple question
Hi, guys, I'm a new comer here. I'm studying Unix Shell and I met a problem confusing me a lot. Here it is :
script 1:
Code:
#!/bin/sh
# scriptname : do_increment
increment(){
	sum=`expr $1 + 1`
	return $sum		# Return the value of sum to the script.
}
echo -n "The sum is "
increment $1			# Call the increment; pass 5 as a parameter.
				# 5 becomes $1 for the increment function.
echo "ha"
echo $?				# The return value is stored in $?.
echo "The sum is $sum"		# The variable 'sum' is known to the function.
				# and is also known to the main script.

Code:
command-line and result 1:
$ ./do_increment 7
The sum is ha
0
The sum is 8

script 2:
Code:
#!/bin/sh
# scriptname : do_increment
increment(){
	sum=`expr $1 + 1`
	return $sum		# Return the value of sum to the script.
}
echo -n "The sum is "
increment $1			# Call the increment; pass 5 as a parameter.
				# 5 becomes $1 for the increment function.
echo $?  # The return value is stored in $?.
echo "ha"				
echo "The sum is $sum"		# The variable 'sum' is known to the function.
				# and is also known to the main script.

command-line and result 2:
Code:
$ ./do_increment 7
The sum is 8
ha
The sum is 8

My question is : why are the results different just because I put the "echo 'ha'" before or after the "echo $?"

Thx a lot!
Last edited by Scott; 05-09-2013 at 12:13 PM.. Reason: Please use code tags and a DESCRIPTIVE subject title
 

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LEARN ABOUT HPUX

sum

sum(1)							      General Commands Manual							    sum(1)

NAME

       sum - print checksum and block or byte count of file(s)

SYNOPSIS

       [file ...]

   Remarks
       is obsolescent and should not be used in new applications that are intended to be portable between systems.  Use instead (see cksum(1)).

DESCRIPTION

       calculates  and	prints to standard output a checksum for each named file, and also prints the size of the file in 512 byte blocks, rounded
       up.

       The default algorithm is a 16-bit sum of the bytes in which overflow is ignored.   Alternate  algorithms  can  be  selected  with  the  and
       options.

       Standard input is used if no file names are given.

       is typically used to verify data integrity when copying files between systems.

   Options
       recognizes the following options:

	      Use an alternate algorithm in which the 16-bit sum is right rotated
			with each byte in computing the checksum.

	      Use the 32-bit cyclical redundancy check (CRC) algorithm used by

RETURN VALUE

       returns the following values upon completion:

	      All files were processed successfully.

	      One or more files could not be read or some other error occurred.

       If an inaccessible file is encountered, continues processing any remaining files, but the final exit status is affected.

DIAGNOSTICS

       Read error conditions are indistinguishable from end of file on most devices; check the block or byte count.

WARNINGS

       This  command  is  likely  to  be withdrawn from X/Open standards.  Applications using this command might not be portable to other vendors'
       platforms. The usage of cksum(1) is recommended.

SEE ALSO

       cksum(1), wc(1).

STANDARDS CONFORMANCE

																	    sum(1)
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