1

When practicing regex in Bash I tried to match the entire set/search-pattern inside the brackets.

Instead, I matched just each single character in them.

For example, with

cd
touch a.c a.h a.o a.cho
ls *.[cho]

The ls matched:

a.c
a.h
a.o 

but it didn't match the entire set as in a.cho.

Why didn't I match the entire set as well and how is it possible to do so?

3

You're not using regular expressions here, but filename globbing patterns.

The [...] will only ever match a single character (this happens to be the same between filename globbing patterns and regular expressions), which is why it does not match the three characters cho ([cho] means "one of c, h and o").

To match all names starting with a. use a.*.

To match all names starting with a. and then directly afterwards ending in either c, h, o or cho, first set the extglob shell option with shopt -s extglob and use a.@([cho]|cho).

A brace expansion like a.{c,h,o,cho} would generate the filenames on the command line, but gives no guarantee that those files actually exists.

  • Oh crap, why do I sometimes call globbing regex. I must stop this forever. But can't we philosophize and say it is a "type" of regex just like JavaScript has it's "type of regex"? I know it's unorthodox, but is it enough false?... – user9303970 Apr 24 '18 at 15:12
  • Can we match all four endings in Bash globbing in one pattern? – user9303970 Apr 24 '18 at 15:13
  • @user9303970 See updated answer. Sorry for mentioning the +(...) pattern before. I rarely use the extended globbing patterns, so I had to do some testing. @(...) is what you may want to use. – Kusalananda Apr 24 '18 at 15:29
  • If you want to match anything that has at least one of those characters after the final dot, use *.+([cho]) (with extglob). That would match any and all of a.c, a.h, a.ch, a.cho etc. – ilkkachu Apr 24 '18 at 16:14
1

You could use bash Brace Expansion which is not a pattern, but a list of strings

ls *.{c,h,o,cho}

The shell expands that before the ls command is executed to

ls *.c *.h *.o *.cho

Since brace expansion occurs before filename expansion, we can put the glob pattern inside the braces

ls *.{[cho],cho}

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