&blen(4)

NAME

&blen, &bmid, &batoi, &bitoa, &bhex, &hexb - Byte functions

SYNOPSIS

&blen str
&bmid str
&batoi str
&bitoa num
&bhex str
&hexb hex

DESCRIPTION

The byte functions work on the bytes of a string, which are the bytes the string would be written to a file as: in a Unicode build the UTF-8 bytes of each character, an invalid byte being that byte and a Nul character the byte 0. In other builds a byte is a character.

Bytes made into a string are decoded as a whole, in a Unicode build valid UTF-8 becomes characters, any other byte an invalid byte and 0 the Nul character.

&blen str


Returns the number of bytes in str.

&bmid str index len


Returns the len bytes of str from byte index (the first byte is 0), negative values work as for &mid(4). A character may be split, its bytes are then invalid bytes.

&batoi str


Returns the value of the first byte of str, 0 if it is empty.

&bitoa num


Returns the byte num as a string, in a Unicode build a byte from 0x80 is an invalid byte.

&bhex str


Returns the bytes of str in lower case hexadecimal, e.g. &bhex "a\xe9" returns "61c3a9" in a Unicode build.

&hexb hex


Returns the string of the bytes given in hexadecimal by hex, it fails if hex holds a non-hexadecimal character or half a byte.

NOTES

As each result is decoded on its own, joining the results of &bitoa gives invalid bytes rather than a UTF-8 character, &bmid of the joined string decodes them together:

&bmid &cat &bitoa 0xc3 &bitoa 0xa9 0 2 

returns an 'e' acute (U+00E9) in a Unicode build, as does &hexb "c3a9".

&blen &lef @wl $window-col gives the byte offset of the cursor in the current line.

EXAMPLE

The following converts a string to its bytes in hexadecimal and back:

set-variable #l0 &bhex "Caf\xe9" 
set-variable #l1 &hexb #l0 

SEE ALSO

&len(4), &mid(4), &atoi(4), &itoa(4), &uni(4).

Ref: &blen(4) File: m4fil039.4 Date: 2026/10/10

(c) Copyright JASSPA 2026