I want to know what this mean.
ps -A
→ Select all processes. Identical to -e.
What's mean "Identical to -e."?
It simply means that the command can be either typed as ps -A
or ps -e
and will produce the same result.
If means that
ps -A
and
ps -e
are the same command.
It is a compatibility issue: in older nonstandartized UNIX systems there were many implementations of commands, and sometimes they used different options for the same things.
From man ps
:
-A Select all processes. Identical to -e. [...] -e Select all processes. Identical to -A.
So, these two options, -A
and -e
, are identical (equivalent) and produce identical results when these are used inside of ps
command and their job is (no matter what option, -A
or -e
, you choose to use) to select all processes when ps
is invoked.
Now, what identical means? From http://dictionary.reference.com/browse/identical:
- similar or alike in every way: The two cars are identical except for their license plates.
- being the very same; selfsame: This is the identical room we stayed in last year.
- agreeing exactly: identical opinions.
Synonyms: congruous, congruent, equal, matching.