FNMATCH(7) Standards, Environments, and Macros FNMATCH(7)

NAME

fnmatch - file name pattern matching

DESCRIPTION

The pattern matching notation described below is used to specify
patterns for matching strings in the shell. Historically, pattern
matching notation is related to, but slightly different from, the regular
expression notation. For this reason, the description of the rules for
this pattern matching notation is based on the description of regular
expression notation described on the regex(7) manual page.

Patterns Matching a Single Character

The following patterns match a single character: ordinary characters,
special pattern characters and pattern bracket expressions. The pattern
bracket expression will also match a single collating element.


An ordinary character is a pattern that matches itself. It can be any
character in the supported character set except for NUL, those special
shell characters that require quoting, and the following three special
pattern characters. Matching is based on the bit pattern used for
encoding the character, not on the graphic representation of the
character. If any character (ordinary, shell special, or pattern special)
is quoted, that pattern will match the character itself. The shell
special characters always require quoting.


When unquoted and outside a bracket expression, the following three
characters will have special meaning in the specification of patterns:

?
A question-mark is a pattern that will match any character.


*
An asterisk is a pattern that will match multiple characters, as
described in Patterns Matching Multiple Characters, below.


[
The open bracket will introduce a pattern bracket expression.


The description of basic regular expression bracket expressions on the
regex(7) manual page also applies to the pattern bracket expression,
except that the exclamation-mark character ( ! ) replaces the circumflex
character (^) in its role in a non-matching list in the regular
expression notation. A bracket expression starting with an unquoted
circumflex character produces unspecified results.


The restriction on a circumflex in a bracket expression is to allow
implementations that support pattern matching using the circumflex as the
negation character in addition to the exclamation-mark. A portable
application must use something like [\^!] to match either character.


When pattern matching is used where shell quote removal is not performed
(such as in the argument to the find -name primary when find is being
called using one of the exec functions, or in the pattern argument to
the fnmatch(3C) function, special characters can be escaped to remove
their special meaning by preceding them with a backslash character. This
escaping backslash will be discarded. The sequence \\ represents one
literal backslash. All of the requirements and effects of quoting on
ordinary, shell special and special pattern characters will apply to
escaping in this context.


Both quoting and escaping are described here because pattern matching
must work in three separate circumstances:

o Calling directly upon the shell, such as in pathname expansion
or in a case statement. All of the following will match the
string or file abc:


abc "abc" a"b"c a\bc a[b]c
a["b"]c a[\b]c a["\b"]c a?c a*c

The following will not:


"a?c" a\*c a\[b]c


o Calling a utility or function without going through a shell,
as described for find(1) and the function fnmatch(3C)

o Calling utilities such as find, cpio, tar or pax through the
shell command line. In this case, shell quote removal is
performed before the utility sees the argument. For example,
in:

find /bin -name e\c[\h]o -print

after quote removal, the backslashes are presented to find and
it treats them as escape characters. Both precede ordinary
characters, so the c and h represent themselves and echo would
be found on many historical systems (that have it in /bin). To
find a file name that contained shell special characters or
pattern characters, both quoting and escaping are required,
such as:

pax -r ... "*a\(\?"

to extract a filename ending with a(?.


Conforming applications are required to quote or escape the shell special
characters (sometimes called metacharacters). If used without this
protection, syntax errors can result or implementation extensions can be
triggered. For example, the KornShell supports a series of extensions
based on parentheses in patterns; see ksh(1)

Patterns Matching Multiple Characters

The following rules are used to construct patterns matching multiple
characters from patterns matching a single character:

o The asterisk (*) is a pattern that will match any string,
including the null string.

o The concatenation of patterns matching a single character is a
valid pattern that will match the concatenation of the single
characters or collating elements matched by each of the
concatenated patterns.

o The concatenation of one or more patterns matching a single
character with one or more asterisks is a valid pattern. In
such patterns, each asterisk will match a string of zero or
more characters, matching the greatest possible number of
characters that still allows the remainder of the pattern to
match the string.


Since each asterisk matches zero or more occurrences, the patterns a*b
and a**b have identical functionality.


Examples:

a[bc]
matches the strings ab and ac.


a*d
matches the strings ad, abd and abcd, but not the string abc.


a*d*
matches the strings ad, abcd, abcdef, aaaad and adddd.


*a*d
matches the strings ad, abcd, efabcd, aaaad and adddd.

Patterns Used for Filename Expansion

The rules described so far in Patterns Matching Multiple Characters and
Patterns Matching a Single Character are qualified by the following rules
that apply when pattern matching notation is used for filename expansion.

1. The slash character in a pathname must be explicitly matched
by using one or more slashes in the pattern; it cannot be
matched by the asterisk or question-mark special characters or
by a bracket expression. Slashes in the pattern are identified
before bracket expressions; thus, a slash cannot be included
in a pattern bracket expression used for filename expansion.
For example, the pattern a[b/c]d will not match such pathnames
as abd or a/d. It will only match a pathname of literally
a[b/c]d.

2. If a filename begins with a period (.), the period must be
explicitly matched by using a period as the first character of
the pattern or immediately following a slash character. The
leading period will not be matched by:

+o the asterisk or question-mark special characters

+o a bracket expression containing a non-matching list, such
as:

[!a]

a range expression, such as:

[%-0]

or a character class expression, such as:

[[:punct:]]

It is unspecified whether an explicit period in a bracket
expression matching list, such as:

[.abc]

can match a leading period in a filename.

3. Specified patterns are matched against existing filenames and
pathnames, as appropriate. Each component that contains a
pattern character requires read permission in the directory
containing that component. Any component, except the last,
that does not contain a pattern character requires search
permission. For example, given the pattern:

/foo/bar/x*/bam

search permission is needed for directories / and foo, search
and read permissions are needed for directory bar, and search
permission is needed for each x* directory.

If the pattern matches any existing filenames or pathnames,
the pattern will be replaced with those filenames and
pathnames, sorted according to the collating sequence in
effect in the current locale. If the pattern contains an
invalid bracket expression or does not match any existing
filenames or pathnames, the pattern string is left unchanged.

SEE ALSO

find(1), ksh(1), fnmatch(3C), regex(7)

June 14, 2015 FNMATCH(7)