Portable Character Set is a set of 103 characters which, according to the POSIX standard, must be present in any character set. Compared to ASCII, the Portable Character Set lacks some control characters, and does not prescribe any particular value encoding. The Portable Character Set is a superset of the Basic Execution Character Set as defined by ANSI C.

name glyph C string Unicode Unicode name NUL   \0 U+0000 NULL (NUL) alert   \a U+0007 ALERT (BEL) backspace   \b U+0008 BACKSPACE (BS) tab   \t U+0009 CHARACTER TABULATION (HT) newline   \n U+000A LINE FEED (LF) vertical-tab   \v U+000B LINE TABULATION (VT) form-feed   \f U+000C FORM FEED (FF) carriage-return   \r U+000D CARRIAGE RETURN (CR) space     U+0020 SPACE exclamation-mark ! ! U+0021 EXCLAMATION MARK quotation-mark " \" U+0022 QUOTATION MARK number-sign # # U+0023 NUMBER SIGN dollar-sign $ $ U+0024 DOLLAR SIGN percent-sign % % U+0025 PERCENT SIGN ampersand & & U+0026 AMPERSAND apostrophe ' \' U+0027 APOSTROPHE left-parenthesis ( ( U+0028 LEFT PARENTHESIS right-parenthesis ) ) U+0029 RIGHT PARENTHESIS asterisk * * U+002A ASTERISK plus-sign + + U+002B PLUS SIGN comma , , U+002C COMMA hyphen - - U+002D HYPHEN-MINUS period . . U+002E FULL STOP slash / / U+002F SOLIDUS zero 0 0 U+0030 DIGIT ZERO one 1 1 U+0031 DIGIT ONE two 2 2 U+0032 DIGIT TWO three 3 3 U+0033 DIGIT THREE four 4 4 U+0034 DIGIT FOUR five 5 5 U+0035 DIGIT FIVE six 6 6 U+0036 DIGIT SIX seven 7 7 U+0037 DIGIT SEVEN eight 8 8 U+0038 DIGIT EIGHT nine 9 9 U+0039 DIGIT NINE colon : : U+003A COLON semicolon ; ; U+003B SEMICOLON less-than-sign < < U+003C LESS-THAN SIGN equals-sign = = U+003D EQUALS SIGN greater-than-sign > > U+003E GREATER-THAN SIGN question-mark ? ? U+003F QUESTION MARK commercial-at @ @ U+0040 COMMERCIAL AT A A A U+0041 LATIN CAPITAL LETTER A B B B U+0042 LATIN CAPITAL LETTER B C C C U+0043 LATIN CAPITAL LETTER C D D D U+0044 LATIN CAPITAL LETTER D E E E U+0045 LATIN CAPITAL LETTER E F F F U+0046 LATIN CAPITAL LETTER F G G G U+0047 LATIN CAPITAL LETTER G H H H U+0048 LATIN CAPITAL LETTER H I I I U+0049 LATIN CAPITAL LETTER I J J J U+004A LATIN CAPITAL LETTER J K K K U+004B LATIN CAPITAL LETTER K L L L U+004C LATIN CAPITAL LETTER L M M M U+004D LATIN CAPITAL LETTER M N N N U+004E LATIN CAPITAL LETTER N O O O U+004F LATIN CAPITAL LETTER O P P P U+0050 LATIN CAPITAL LETTER P Q Q Q U+0051 LATIN CAPITAL LETTER Q R R R U+0052 LATIN CAPITAL LETTER R S S S U+0053 LATIN CAPITAL LETTER S T T T U+0054 LATIN CAPITAL LETTER T U U U U+0055 LATIN CAPITAL LETTER U V V V U+0056 LATIN CAPITAL LETTER V W W W U+0057 LATIN CAPITAL LETTER W X X X U+0058 LATIN CAPITAL LETTER X Y Y Y U+0059 LATIN CAPITAL LETTER Y Z Z Z U+005A LATIN CAPITAL LETTER Z left-square-bracket [ [ U+005B LEFT SQUARE BRACKET backslash \ \\ U+005C REVERSE SOLIDUS right-square-bracket ] ] U+005D RIGHT SQUARE BRACKET circumflex ^ ^ U+005E CIRCUMFLEX ACCENT underscore _ _ U+005F LOW LINE grave-accent ` ` U+0060 GRAVE ACCENT a a a U+0061 LATIN SMALL LETTER A b b b U+0062 LATIN SMALL LETTER B c c c U+0063 LATIN SMALL LETTER C d d d U+0064 LATIN SMALL LETTER D e e e U+0065 LATIN SMALL LETTER E f f f U+0066 LATIN SMALL LETTER F g g g U+0067 LATIN SMALL LETTER G h h h U+0068 LATIN SMALL LETTER H i i i U+0069 LATIN SMALL LETTER I j j j U+006A LATIN SMALL LETTER J k k k U+006B LATIN SMALL LETTER K l l l U+006C LATIN SMALL LETTER L m m m U+006D LATIN SMALL LETTER M n n n U+006E LATIN SMALL LETTER N o o o U+006F LATIN SMALL LETTER O p p p U+0070 LATIN SMALL LETTER P q q q U+0071 LATIN SMALL LETTER Q r r r U+0072 LATIN SMALL LETTER R s s s U+0073 LATIN SMALL LETTER S t t t U+0074 LATIN SMALL LETTER T u u u U+0075 LATIN SMALL LETTER U v v v U+0076 LATIN SMALL LETTER V w w w U+0077 LATIN SMALL LETTER W x x x U+0078 LATIN SMALL LETTER X y y y U+0079 LATIN SMALL LETTER Y z z z U+007A LATIN SMALL LETTER Z left-brace { { U+007B LEFT CURLY BRACKET vertical-line U+007C VERTICAL LINE right-brace } } U+007D RIGHT CURLY BRACKET tilde ~ ~ U+007E TILDE

Character Classes Characters grouped by their class. (facsimile, not machine readable)

Unicode range Character Class POSIX.1-2017 Standard U+0000 Control Portable U+0001 to U+0006 Control Non-Portable U+0007 to U+0008 Control Portable U+0009 to U+000D White-space Portable U+0010 to U+001F Control Non-Portable U+0020 White-space Portable U+0021 to U+002F Punctuation Portable U+0030 to U+0039 Digit Portable U+003A to U+0040 Punctuation Portable U+0041 to U+005A Uppercase Letter Portable U+005B to U+0060 Punctuation Portable U+0061 to U+007A Lowercase Letter Portable U+007B to U+007E Punctuation Portable U+007F Control Non-Portable

Portable filename character set

POSIX also standardizes a portable filename character set, a much smaller subset of 65 of the above characters:Open Group. "Portable Filename Character Set". 26 uppercase letters, 26 lowercase letters, 10 decimal digits, and three punctuation characters "period", "underscore", and "hyphen".

To be usable across all POSIX locales, a pathname should consist only of characters from that portable filename character set, "slash" characters, and a single final "NUL" character.Open Group. "Pathname". Like the Portable Character Set that these characters are taken from, the encoding of the portable filename character set is not specified.Dave Johnson. "Concepts of C/UNIX Internationalization". "File Names".

To be usable across all POSIX locales, user names, group names, file names, and directory names should be composed only from characters from the portable filename character set. The "hyphen" should not be used as the first character of any of those names.

Many people recommend using only this portable filename character set for file names and directory names, even on systems that technically could use other letters and symbols; perhaps by using utilities such as detox, convmv, and Glindra to fix "bad" filenames.David A. Wheeler. "Fixing Unix/Linux/POSIX Filenames: Control Characters (such as Newline), Leading Dashes, and Other Problems".IBM z/OS documentation. "Opening files".The Linux Information Project. "File Naming Conventions in Linux".Michigan Tech. "Characters to Avoid in Filenames and Directories"

References