Unix & Linux Stack Exchange is a question and answer site for users of Linux, FreeBSD and other Un*x-like operating systems. It only takes a minute to sign up.
Sign up to join this community
We know that the backtick character is used for command substitution:
chown `id -u` /mydir
Which made me wonder: is the tick character ´ used for anything in the Linux shell?
Note: incidentally, command substitution can also be written more readably as
chown $(id -u) /mydir
The character sets used historically with Unix, including ASCII, don’t have a tick character, so it wasn’t used. As far as I’m aware no common usage for that character has been introduced since it’s become available; nor would it, since it’s not included in POSIX’s portable character set.
` was apparently originally included in ASCII (along with ^ and ~) to serve as a diacritic. When ASCII was defined, the apostrophe was typically represented by a ′-style glyph (“prime”, as used for minutes or feet) rather than a straight apostrophe ', and was used as a diacritic acute accent too.
Historically, in Unix shell documentation, ` was referred to as a grave accent, not a backtick. The lack of a forward tick wouldn’t have raised eyebrows, especially since ' was used as the complementary character (see roff syntax).
´ is 0xB4 in a fr_FR.iso88591 locale, 0xC2 0xB4 in a fr_FR.UTF-8 and doesn't exist in the C locale.
Nov 2, 2018 at 10:10
fr_FR is replaced with any other language. The encoding of the character is a property of the encoding (ISO-8859-1 or UTF-8).
fr_FR was arbitrary, it just happens I have such locales on my system. Of course it would be the same with en_GB.UTF-8...
Nov 2, 2018 at 17:05
Although the ASCII committee thought of ` as a diacritic and ' as an apostrophe, the Unix tradition was to treat them as left and right single quotes (the characters that are now in Unicode as U+2018 and U+2019). This is most obvious from the TeX convention that you write ``quoted text'' in the markup source and you get “quoted text” in the formatted document. This can also be seen in older monospace fonts, such as the bitmap fonts shipped with X11R5 and X11R6, where the two characters were given mirror-image glyphs.
As such, ` and ' were considered each others' inverse, and ´ was not felt to be missing.
' was explicitly defined in ASCII as APOSTROPHE, RIGHT SINGLE QUOTATION MARK, ACUTE_ACCENT by ANSI, it's not only a Unix thing. There is no other right single quotation mark in ASCII.
Nov 2, 2018 at 16:35
´is called acute accent only when used as a diacritic (and, conversely,`is called grave accent). When used alone, as the latter is a backtick, it seemed natural for the former to be called a tick or forward tick (please let's not call it reverse backtick). I've modified the title question to include your note.', ASCII 39, U+0027) has meaning in many of the Unix shells (e.g. the Bourne shell/bin/sh) and Linux shells (e.g./bin/bash). It prevents words splitting and all expansions. Sols '$foo [bar]'returns an error unless there is a file named$foo [bar]in the current directory. It's equvalent tols "\$foo [bar]"andls \$foo\ \[bar\].',",`) have special meaning in Unix shells.