mirror of
https://github.com/topjohnwu/ndk-busybox.git
synced 2024-11-30 15:10:36 +00:00
647553a4fc
function old new delta expand_vars_to_list 2129 2197 +68 Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
51 lines
2.6 KiB
Plaintext
51 lines
2.6 KiB
Plaintext
Brace Expansion
|
|
|
|
Brace expansion is a mechanism by which arbitrary strings may be gener-
|
|
ated. This mechanism is similar to pathname expansion, but the file-
|
|
names generated need not exist. Patterns to be brace expanded take the
|
|
form of an optional preamble, followed by either a series of comma-sep-
|
|
arated strings or a sequence expression between a pair of braces, fol-
|
|
lowed by an optional postscript. The preamble is prefixed to each
|
|
string contained within the braces, and the postscript is then appended
|
|
to each resulting string, expanding left to right.
|
|
|
|
Brace expansions may be nested. The results of each expanded string
|
|
are not sorted; left to right order is preserved. For example,
|
|
a{d,c,b}e expands into `ade ace abe'.
|
|
|
|
A sequence expression takes the form {x..y}, where x and y are either
|
|
integers or single characters. When integers are supplied, the expres-
|
|
sion expands to each number between x and y, inclusive. When charac-
|
|
ters are supplied, the expression expands to each character lexico-
|
|
graphically between x and y, inclusive. Note that both x and y must be
|
|
of the same type.
|
|
|
|
Brace expansion is performed before any other expansions, and any char-
|
|
acters special to other expansions are preserved in the result. It is
|
|
strictly textual. Bash does not apply any syntactic interpretation to
|
|
the context of the expansion or the text between the braces.
|
|
|
|
A correctly-formed brace expansion must contain unquoted opening and
|
|
closing braces, and at least one unquoted comma or a valid sequence
|
|
expression. Any incorrectly formed brace expansion is left unchanged.
|
|
A { or , may be quoted with a backslash to prevent its being considered
|
|
part of a brace expression. To avoid conflicts with parameter expan-
|
|
sion, the string ${ is not considered eligible for brace expansion.
|
|
|
|
This construct is typically used as shorthand when the common prefix of
|
|
the strings to be generated is longer than in the above example:
|
|
|
|
mkdir /usr/local/src/bash/{old,new,dist,bugs}
|
|
or
|
|
chown root /usr/{ucb/{ex,edit},lib/{ex?.?*,how_ex}}
|
|
|
|
Brace expansion introduces a slight incompatibility with historical
|
|
versions of sh. sh does not treat opening or closing braces specially
|
|
when they appear as part of a word, and preserves them in the output.
|
|
Bash removes braces from words as a consequence of brace expansion.
|
|
For example, a word entered to sh as file{1,2} appears identically in
|
|
the output. The same word is output as file1 file2 after expansion by
|
|
bash. If strict compatibility with sh is desired, start bash with the
|
|
+B option or disable brace expansion with the +B option to the set com-
|
|
mand
|