Bash
└─ Brace expansion

In Bash, brace expansion is a mechanism by which arbitrary strings may be generated.

It has two forms:

1. Comma-separated strings.

   For example, a{d,c,b}e expands to ade ace abe.

2. Sequence expression.

   For example,

   • S{1..4} expands to S1 S2 S3 S4;
   • {0..4..2} expands to 0 2 4;
   • {a..f} expands to a b c d e f.

Brace expansions can be combined. For example, {a..b}{1..2} expands to a1 a2 b1 b2.

Brace expansions tend to be most useful when dealing with file paths (especially if the paths are long and some of the files don't exist yet). For example, mv /long/path/to/file_{old,new}.

See man bash for more information.