can anyone tell me how to replicate the seq command using a bash shell script ?

What exactly is the seq command?

Cheers,
Tink

seq() { a="$1"; while [ "$a" -le "$2" ]; do echo "$a"; ((a++)); done; }

i dont understand im sorry im newbie. so how would you input the numbers to be seq.??

that wouyld be the contents of a script file, so you can save it as seq2 or something, and use it in the same way.

now i made a few changes
{ a="$1"; while [ "$a" -le "$2" ]; do echo "$a"; ((a=$a+$2)); done; }
it works fine when i enter three positive numbers but dosent work with negative numbers. Any clues for a newbie student. ??

pls. help me

Smells like homework to me. Why would you want to do this in a bash script when the seq command itself is something that's commonly used in bash scripts?

well like you said its homework. We need to duplicate the functionality of the seq command with a script . I need to use a determinate loop and pasrse the command line input variables for accuracy. Should the user enter the wrong number, or type, of variables it needs to display an error message and needs to support .
--help: displays help and exits
--version: display the help screen and the version number

I am so lost im just know understanding the basic stuff

hope someone can help

klfreese:

I think the problem here is the questions you're asking. If it's homework, the last thing you should ask is "how do I do this?". What good does it do you to have someone else do it for you?

Perhaps you might consider asking questions to help you learn how to do it yourself.

First is understanding how to use command line options. They are stored in variables $1, $2, $3, $4, etc.
Second is knowing how to test the command line args to see if they hold legitimate values, or enough were given. Here's the bash how-to on condionals: http://www.tldp.org/LDP/abs/html/comparison-ops.html

Third, is knowing how to do loops. Here is the bash how-to on loops: http://www.tldp.org/LDP/abs/html/loops.html

Fourth, is knowing how to do variable arithmetic. here is the bash how-to with some examples: http://www.tldp.org/LDP/abs/html/arithexp.html

If you're really confused on where to start, then do this:
Write out the steps that you think you have to go through in order to accomplish this task. Don't worry about writing code, just write it out. Then, if you aren't sure of the logic, post what you have, and ask for comments on the logic. We all will be more than happy to help you learn how to fix the logic.

Then, write your first rev of the code. Be patient and try to get the various aspects of it to work. If you're really stuck, then post your code, and we'll help you learn how to find the problems and fix them.

That should be enough to get you going.

This is what i have so far it work but wont work with the 1st or second param being a neg number any sugestions ?



#!/bin/bash
#
#
HOWTO="How To: ./seq P1 P2 P3 "
#
VERSION="Number Sequencer"
#
[ "$1" = "--version" ] && echo $HOWTO && echo $VERSION && exit
#
[ "$1" = "--help" ] || [ $# -ne 3 ] && echo "$HOWTO" && exit 1
#
[ $2 -eq 0 ] && echo "Parameter 2 can not be 0 - ABORT" && exit 2
#
{ a="$1"; while [ "$a" -le "$3" ]; do echo "$a"; ((a=$a+$2)); done; }
#
{ a="$1"; while [ "$a" -ge "$3" ]; do echo "$a"; ((a=$a-$2)); done; }

It worked as is except the last line has a typo:
{ a="$1"; while [ "$a" -ge "$3" ]; do echo "$a"; ((a=$a-$2)); done; }

Should be like this:
{ a="$1"; while [ "$a" -ge "$3" ]; do echo "$a"; ((a=$a+$2)); done; }
You should still add the numbers because the increment should be negative and, if you subtract a negative you are adding!

You might also want to put in a couple more tests on the P1 P2 P3 parameters like the real seq:

[ $1 -gt $3 ] && [ $2 -gt 0 ] && echo "When the starting value is greater than the limit, the increment must be negative." && exit 3
[ $1 -lt $3 ] && [ $2 -lt 0 ] && echo "When the starting value is less than the limit, the increment must be positive." && exit 4

<edit> oops

please DO NOT ask homework question son this site, you are set homework for a reason. cheating is bad mmmmmmmmmkay?

i'd also thank members for not replying to questions about homework in future (even though it is obviously in good nature)

Yeah! From now on if someone asks you if this is homework the correct reply is "No this is just something I'm tinkering with."