mjhjmtu

I would like to copy the files, located on a remote machine, whose filenames match a prefix string, on my local machine.

I have tried to select only the files whose names start with either massif or calgrind using the following command:

scp my-machine:/home/user/a-folder/[massif,callgrind]* .

However, this expression allows to match the empty string plus any number of characters and therefore, matches all the filenames related to the directory.

What do I have to change to make it work correctly?

It sounds like you want curly-brackets there:

scp my-machine:/home/user/a-folder/massif,callgrind* .

Otherwise you're matching on single characters, rather than the two complete strings.

bash does a number of different types of expansion & substitution; these are documented in the bash man page - looks for the EXPANSION section. Here, the [ type is covered under "Pathname Expansion" (it matches on pathnames) and { under "Brace Expansion" (it generates multiple arguments from the options provided, regardless of files present).

Bash provides some extended patterns if the extglob shell option is enabled (c.f. Bash Reference Manual).

prompt% ssh username@hostname echo 'shopt -s extglob >>~/.bash_profile'
prompt% scp username@hostname:"/home/user/dirname/@(foo|bar)*" .

The first command enables the extglob shell option on the remote host. The second command allows to copy filenames that begin with foo or bar in the current directory of the local machine.

Note: I recommend editing the configuration file .bash_profile manually. The double quotes are necessary to avoid the interpretation of the filename expansion by the local shell.