UNIX for Advanced & Expert Users

what i want to be is that i would like to reinvent new options that have the same functionality as
...
-u is the same functionality of conv=ucase
and -l have the same functionality as conv=lcase...

is there a way that i can put these in my script so that
whenever i will typed in command line such as

Code:

dd if=file of=file.new -u

so that the file contents will become upper case ... Please need help....

Moderator's Comments:

please use code tags

For the amount of work you need to do the return is minimal. And there is no such thing as 'adding an option' without doing a lot of coding. Also, if you use /usr/bin/dd instead of just plain dd, you will get the old behavior, not what you want.

1. create a script that turns -l into conv=lcase and -u into conv=lcase

Code:

#!/bin/bash
cmd="$*" 
cmd= cmd=$( echo "$cmd" |  sed 's/dd /\/usr\/bin\/dd /'| sed 's/\-u/conv=ucase /' | sed  's/\-l/conv=lcase /' )
eval $cmd

Be sure to add execute permissions to you new script:

Code:

chmod +x nameofnewscript

2. edit your login .profile or .bashrc file to create an alias for the script

Code:

alias dd=/path/to/mydd.shl

3. log out and then back in, your new alias will be shown in the output of:

Code:

alias

As an aside I don't see why you'd want to go to all this trouble....

ok thank you very much for your great help... i will try this later after my class... thanks and god bless

Just for clarity here (there is absolutely no critical intent) - when using sed and there are a lot of escaped slashes I use a different separator - to make things easier to read.

Code:

#!/bin/bash
cmd="$*" 
cmd= cmd=$( echo "$cmd" |  sed 's/dd /\/usr\/bin\/dd /'| sed 's/\-u/conv=ucase /' | sed  's/\-l/conv=lcase /' )
eval $cmd

I would enter that as follows.

Code:

#!/bin/bash
cmd="$*" 
cmd= cmd=$( echo "$cmd" |  sed 's;dd ;/usr/bin/dd ;'| sed 's;\-u;conv=ucase ;' | sed  's;\-l;conv=lcase ;' )
eval $cmd

You can use any character that you want here, as I said just improves readability IMHO.

Regards

Dave

Code:

I would use a function called dd() and call /bin/dd inside it after substituting the options

I would do none of the above. IMO: There is no discernable purpose (other than homework which this now appears to be) to doing any of this.

There are instances for using an alias (or a function) when for security reasons you want to do something like flip off/on ftp or sftp without breaking anything. Not because you want to spend cpu cycles so you can type "-u" instead of "conv=ucase"

Does anybody remember trigraphs in C? They came about because some early keyboards could not create certain characters. There had to be a workaround. Doing this "entry workaround" kind of thing is not inherently purposeless.

Since I cannot tell if this is homework, I'm leaving the thread open. Another mod may not do that.

i try this at home and theres a problem...
the name of my script is mydd
and i do the above like what it is said... but when i type in command line
bash@ubuntu$: dd if=mydd of=mydd.new -u
bash@ubuntu$: /path/to/mydd.sh file or directory not found


why is it??