How does one create a wrapper around a program?

Question

I want to learn to create a wrapper around a program in linux. How does one do this? A tutorial reference web-page/link or example will do. To clarify what I want to learn, I will explain with an example.

I use vim for editing text files. And use rcs as my simple revision control system. rcs allows you to check-in and checkout-files. I would like to create a warpper program named vir which when I type in the shell as:

$ vir temp.txt

will load the file temp.txt into rcs with ci -u temp.txt and then allows me to edit the file using vim.

When I get out and go back in, It will need to check out the file first, using ci -u temp.txt and allow me to edit the file as one normally does with vim, and then when I save and exit, it should check-in the file using co -u temp.txt and as part of that I should be able to add a version control comment.

Basically, all I want to be doing on the command line is:

$ vir temp.txt

as one would with vim. And the wrapper should take care of the version control for me.

This is generally what aliases, functions, scripts, or compiled programs are for. Any way you can write a program, you can probably do this. — D. Ben Knoble, Oct 27 '19 at 15:13

score 0 · Answer 1 · answered Oct 27 '19 at 14:25

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Take a look at rcsvers.vim, a vim plugin for automatically saving versions in RCS; you could modify that. There are also other RCS plugins for vim at vim.org

answered Oct 27 '19 at 14:25

rpilkey

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Thank you. I will look into the plugins as that will provide better functionality than I am likely to create for myself. I still want to learn how to create a wrapper myself though, so I would like to learn that as well. – Kris Matrix Oct 28 '19 at 15:26

SergioAraujo · Answer 2 · 2019-10-27T21:56:09.590

I have a wrapper to enhance the ping command (using zsh) it could, maybe help you:

# ping command wrapper - Last Change: out 27 2019 18:47
# source: https://www.cyberciti.biz/tips/unix-linux-bash-shell-script-wrapper-examples.html
ping(){
    # Name: ping() wrapper
    # Arg: (url|domain|ip)
    # Purpose: Send ping request to domain by removing urls, protocol, username:pass using system /usr/bin/ping
    local array=( $@ )          # get all args in an array
    local host=${array[-1]}     # get the last arg
    local args=${array[1,-2]}   # get all args before last arg in $@
    #local _ping="/usr/bin/ping"
    local _ping="/bin/ping"
    local c=$(_getdomainnameonly "$host")
    [ "$host" != "$c" ] && echo "Sending ICMP ECHO_REQUEST to \"$c\"..."
    # pass args and host
    # $_ping $args $c
    # default args for ping
    $_ping -n -c 2 -i 1 -W1 $c
}

_getdomainnameonly(){
    # Name: _getdomainnameonly
    # Arg: Url/domain/ip
    # Returns: Only domain name
    # Purpose: Get domain name and remove protocol part, username:password and other parts from url
    # get url
    local h="$1"
    # upper to lowercase
    local f="${h:l}"
    # remove protocol part of hostname
    f="${f#http://}"
    f="${f#https://}"
    f="${f#ftp://}"
    f="${f#scp://}"
    f="${f#scp://}"
    f="${f#sftp://}"
    # Remove username and/or username:password part of hostname
    f="${f#*:*@}"
    f="${f#*@}"
    # remove all /foo/xyz.html*
    f=${f%%/*}
    # show domain name only
    echo "$f"
}

What it hides the local ping using a function called "ping", so if your script has precedence on your path it will find at first the function ping. Then inside the script I define an internal variable called ping that points out to the real ping command:

 local _ping="/bin/ping"

You can also notice that the args are stored in one array.

I think this is what I want. Is this C code or is it bash? It looks like it is bash. I need to an explanation/elaboration on what these lines of code are doing: `local _ping="/bin/ping" #it seems like $_ping gets replaced by /bin/ping. Is this true in c?` `local c=$(_getdomainnameonly "$host") #looks like you are doing an eval of sorts. where you are calling the function getdomainnameonly() and passing variable $host` `$_ping -n -c 2 -i 1 -W1 $c #assume -n, -c 2, -i 1, -W1 are standard ping flags?` — Kris Matrix, Oct 28 '19 at 15:36
I have never tested this code in "C" but yes, $_ping replaces `/bin/ping`. The getdomainnameonly gets rid of everything but the domain of the target site. As long as I have written this code a long time ago, but these are to make the ping faster. — SergioAraujo, Oct 31 '19 at 18:41

How does one create a wrapper around a program?

2 Answers2