brace

Command grouping (current shell)

$ { [command1]; [command2]; }

$ echo {a,b,c}

$ echo {1..10}

$ echo ${var}

$ touch file{1,2,3}.txt

{ commands; }
{a,b,c}
{start..end}
${parameter}

{ } (braces/curly brackets) serve multiple purposes in shell:
Command grouping: { cmd1; cmd2; } groups commands to run in the current shell (unlike (...) which uses a subshell). Requires spaces after { and ; before }.
Brace expansion: {a,b,c} expands to a b c. Useful for generating lists:
- file{1,2,3} → file1 file2 file3
- {a..z} → alphabet
- {1..10} → numbers 1-10
- {01..10} → zero-padded: 01 02 ... 10
Parameter expansion: ${var} accesses variables, required for:
- Array access: ${array[0]}
- Modifiers: ${var:-default}
- Disambiguation: ${var}text

Command grouping requires space after { and semicolon before }: { cmd; } not {cmd}.
Brace expansion is not glob expansion - it happens before other expansions and doesn't check if files exist.
{} in find commands is the replacement string, not brace expansion.

bash(1), sh(1), zsh(1)