问题
If we define and use an alias B within another alias A, the first time execution of A will fail. For example,
alias A='alias B="which ls"; B;'
The first time excution would look like (in bash)
bash: B: command not found
The example above is a simplified construction. in practice, we might meet such usage implicitly.
The reason might be: when we execute the alias A, all expansions are carried out before execution, but B is undefined when we execute A for the first time.
So is there a way to make the first time execution successful?
The situation I met is more complex than above. My alias looks like (in tcsh)
alias A 'cmd1; cmd2; B -v arg_of_B; cmd3; cmd4;'
where, B is an alias defined by cmd2. In addition, the definition of B looks like (in tcsh)
alias B 'source /path/to/script.csh'
So using eval to postpone the execution of B might not work, because eval will fork a new shell to execute the command. Another factor making this more complex is there are arguments following the alias. I tried to use exec but without achieving success.
回答1:
The problem can be simplified to a simple alias. The following fails for the first time as well:
alias A=ls ; A
To postpone the expansion, you can use eval:
alias A=df ; eval A
(Tested in bash and tcsh).
来源：https://stackoverflow.com/questions/16459920/a-newly-defined-alias-within-another-alias-the-first-excution-will-fail