Manpages - vis.3bsd

(See

for include usage.)

The

function copies into

a string which represents the character

needs no encoding, it is copied in unaltered. The string is null terminated, and a pointer to the end of the string is returned. The maximum length of any encoding is four bytes (not including the trailing

thus, when encoding a set of characters into a buffer, the size of the buffer should be four times the number of bytes encoded, plus one for the trailing

The flag parameter is used for altering the default range of characters considered for encoding and for altering the visual representation. The additional character,

is only used when selecting the

encoding format (explained below).

The

and

functions copy into

a visual representation of the string

The

and

functions encode characters from

up to the first

The

and

functions encode exactly

characters from

(this is useful for encoding a block of data that may contain

Both forms

terminate

The size of

must be four times the number of bytes encoded from

(plus one for the

Both forms return the number of characters in

(not including the trailing

The

function allocates space dynamically to hold the string. The

versions of the functions also take an additional argument

that indicates the length of the

buffer. If

is not large enough to fit the converted string then the

and

functions return -1 and set

The

function takes an additional argument,

that is used to pass in and out a multibyte conversion error flag. This is useful when processing single characters at a time when it is possible that the locale may be set to something other than the locale of the characters in the input data.

The functions

and

correspond to

and

but have an additional argument

pointing to a

terminated list of characters. These characters will be copied encoded or backslash-escaped into

These functions are useful e.g. to remove the special meaning of certain characters to shells.

The encoding is a unique, invertible representation composed entirely of graphic characters; it can be decoded back into the original form using the

functions.

There are two parameters that can be controlled: the range of characters that are encoded (applies only to

and

and the type of representation used. By default, all non-graphic characters, except space, tab, and newline are encoded (see

The following flags alter this:

Also encode double quotes

Also encode the magic characters

and

recognized by

Also encode the meta characters used by shells (in addition to the glob characters):

and

Also encode space.

Also encode tab.

Also encode newline.

Synonym for

Only encode

characters. Unsafe means control characters which may cause common terminals to perform unexpected functions. Currently this form allows space, tab, newline, backspace, bell, and return — in addition to all graphic characters — unencoded.

(The above flags have no effect for

and

When using these functions, place all graphic characters to be encoded in an array pointed to by

In general, the backslash character should be included in this array, see the warning on the use of the

flag below).

There are six forms of encoding. All forms use the backslash character

to introduce a special sequence; two backslashes are used to represent a real backslash, except

that uses

These are the visual formats:

Use an

to represent meta characters (characters with the 8th bit set), and use caret

to represent control characters (see

The following formats are used:

Represents the control character

Spans characters

through

and

(as

Represents character

with the 8th bit set. Spans characters

through

Represents control character

with the 8th bit set. Spans characters

through

and

(as

Represents

space.

Represents Meta-space.

Use C-style backslash sequences to represent standard non-printable characters. The following sequences are used to represent the indicated characters:

When using this format, the

parameter is looked at to determine if a

character can be encoded as

instead of

is an octal digit, the latter representation is used to avoid ambiguity.

Non-printable characters without C-style backslash sequences use the default representation.

Use a three digit octal sequence. The form is

where

represents an octal digit.

Same as

except that non-printable characters without C-style backslash sequences use a three digit octal sequence.

Use URI encoding as described in RFC 1738. The form is

where

represents a lower case hexadecimal digit.

Use MIME Quoted-Printable encoding as described in RFC 2045, only don’t break lines and don’t handle CRLF. The form is

where

represents an upper case hexadecimal digit.

There is one additional flag,

which inhibits the doubling of backslashes and the backslash before the default format (that is, control characters are represented by

and meta characters as

With this flag set, the encoding is ambiguous and non-invertible.

These functions support multibyte character input. The encoding conversion is influenced by the setting of the

environment variable which defines the set of characters that can be copied without encoding.

is set, processing is done assuming the C locale and overriding any other environment settings.

When 8-bit data is present in the input,

must be set to the correct locale or to the C locale. If the locales of the data and the conversion are mismatched, multibyte character recognition may fail and encoding will be performed byte-by-byte instead.

As noted above,

must be four times the number of bytes processed from

But note that each multibyte character can be up to

bytes so in terms of multibyte characters,

must be four times

times the number of characters processed from

Specify the locale of the input data. Set to C if the input data locale is unknown.

The functions

and

will return

and the functions

and

will return -1 when the

destination buffer size is not enough to perform the conversion while setting

to:

The destination buffer size is not large enough to perform the conversion.

The

and

functions first appeared in

The

and

functions appeared in

The buffer size limited versions of the functions

and

appeared in

and

Multibyte character support was added in

and