If a run the watch command containing an alias, it will not expand the alias. I have tried both with single quote and double quotes, in fact given the following alias:
# alias ll
alias ll='ls -l --color=tty'
The following command will fail
# watch ll
sh: ll: command not found
Shouldn't command line expansion work in this case?
Aliases are only expanded as the first argument, or after another alias with a trailing space on the end of the command.
From bash's help alias:
A trailing space in VALUE causes the next word to be checked for alias substitution when the alias is expanded.
To do this, try the following:
alias watch='watch '
alias ll='ls -l --color=tty'
watch ll
Bear in mind that some versions of watch strip colours by default, on some versions this can be stopped by using --color or -G.
watch because the alias has to be the next word, whereas watch needs its arguments before the command to run. If you tried watch -n 10 <alias>, bash won't expand the alias. To work around it, you need an alias that includes the options you want (e.g., `alias watch-10='watch -n 10 '), still with a trailing space.
– indiv
Jul 10 '17 at 19:46
I thought here basic problem is while executing watch, the argument is given to "sh -c" which means if alias ll is not defined in sh(dash shell's) environment then it will not expand it. But I was wrong and this is not the case, Chris' answer above is right.
watch 'alias ll="ls -l --color=tty"; type ll; ll'.
– Chris Down
Nov 25 '11 at 12:54
sh -c" the your explanation is applicable for sh too. Am I right?
– Sachin Divekar
Nov 25 '11 at 13:02
sh. Notice that this does work: sh -c $'alias ll="ls -l --color=tty"\ntype ll\nll'
– Chris Down
Nov 25 '11 at 13:10
