Also encode magic characters ‘(*’, ‘?’, ‘[’ and ‘#’) recognized by glob(3).
VIS_SP
Also encode space.
VIS_TAB
Also encode tab.
VIS_NL
Also encode newline.
VIS_WHITE
Synonym for VIS_SP | VIS_TAB | VIS_NL.
VIS_SAFE
Only encode "unsafe" 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.
There are four forms of encoding. Most forms use the backslash character ‘\’ to introduce a special sequence; two backslashes are used to represent a real backslash. These are the visual formats:
(default)
Use an ‘M’ to represent meta characters (characters with the 8th bit set), and use caret ‘^’ to represent control characters see ( iscntrl(3)). The following formats are used:
\^C
Represents the control character ‘C’. Spans characters ‘\000’ through ‘\037’, and ‘\177’ (as ‘\^?’).
\M-C
Represents character ‘C’ with the 8th bit set. Spans characters ‘\241’ through ‘\376’.
\M^C
Represents control character ‘C’ with the 8th bit set. Spans characters ‘\200’ through ‘\237’, and ‘\377’ (as ‘\M^?’).
\040
Represents ASCII space.
\240
Represents Meta-space.
VIS_CSTYLE
Use C-style backslash sequences to represent standard non-printable characters. The following sequences are used to represent the indicated characters:
\a
BEL (007)
\b
BS (010)
\f
NP (014)
\n
NL (012)
\r
CR (015)
\t
HT (011)
\v
VT (013)
\0
NUL (000)
When using this format, the nextc argument is looked at to determine if a NUL character can be encoded as ‘\0’ instead of ‘\000’. If nextc is an octal digit, the latter representation is used to avoid ambiguity.
VIS_HTTPSTYLE
Use URI encoding as described in RFC 1808. The form is ‘%dd’ where d represents a hexadecimal digit.
VIS_OCTAL
Use a three digit octal sequence. The form is ‘\ddd’ where d represents an octal digit.
There is one additional flag, VIS_NOSLASH, which inhibits the doubling of backslashes and the backslash before the default format (that is, control characters are represented by ‘^C’ and meta characters as ‘M-C’). With this flag set, the encoding is ambiguous and non-invertible.
