Re: alias not working

[alex xmb ratchev]

On Wed, Apr 26, 2023, 19:34 Greg Wooledge <greg@wooledge.org> wrote:

> On Wed, Apr 26, 2023 at 12:21:09PM -0500, Mike McClain wrote:
> > I have a non-standard calender file with entries like this:
> >
> > May 5 '23       Fri 1900    next TASCA dance
> >
> > May 6 '23       Sat 1800    Cherokee Co. barn dance, CC Expo
> >
> > I have an alias 'mo' defined as so:
> >
> > alias mo='m=$(command date "+%b");
> >     echo; echo Today is $(command date "+%a %-d %b. %Y %-k:%M");
> >     if [ -z "$1" ]; then
> >         egrep "^$m" calendar;
> >     else
> >         egrep "^$1" calendar;
> >     fi'
>
> Aliases don't take arguments.  "$1" inside this alias will simply be
> the script's $1, or your interactive shell's $1, which is very likely
> the empty string.
>
> What you want is a function.  Functions can be given arguments, which
> are accessed as positional parameters ($1 and so on).
>
> unalias mo
> mo() {
>     printf '\nToday is %s\n' "$(date '+%a %-d %b. %Y %-k:%M')"
>     if [ -z "$1" ]; then
>         local m=$(date +%b)
>         egrep "^$m" calendar
>     else
>         egrep "^$1" calendar
>     fi
> }
>

egrep "^${1:+$m}" .file

I'll also point out, for the record, two improvements that can be made
> here.
>
> 1) The printf command can generate timestamps without needing to call
>    date(1).  I'm not sure if all of your date arguments have corresponding
>    printf %(...)T specifiers, but generally speaking you can get most
>    of what you want without calling date.
>
> 2) Calling date twice in the same function/script can lead to different
>    results, if time passes between the two calls, or if the system clock
>    jumps forward, or if you run the program right before midnight, etc.
>    It's best to get all of the fields you need in a single call to date
>    (or printf %()T), and parse them out as needed.
>
>