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This chapter describes "mini-languages" like glob patterns and brace expansion.

In contrast, the main sub languages of YSH are command, word, and expression.

(in progress)

Other Shell Sublanguages

Arithmetic

arith-context

Arithmetic expressions are parsed and evaluated in many parts of POSIX shell and bash.

Static:

a=$(( x + 1 ))  # POSIX shell

# bash
(( a = x + 1 ))

for (( i = 0; i < n; ++i )); do
  echo $i
done

Dynamic:

[[ 5 -eq 3+x ]]   # but not test  5 -eq 3+x

Array index contexts:

echo ${a[i+1]}      # get
echo ${#a[i+1]}     # calculate

a[i+1]=foo          # set

test -v 'a[i+1]'    # is item set?
[[ -v 'a[i+1]' ]]   # is item set?

printf -v 'a[i+1]'  # assign to this location
unset 'a[i+1]'      # unset location

echo ${a[@] : i+1 : i+2 }  # bash slicing

sh-numbers

sh-arith

sh-logical

sh-bitwise

Boolean

bool-expr

bool-infix

bool-path

bool-str

bool-other

Patterns

glob-pat

TODO: glob syntax

extglob

TODO: extended glob syntax

regex

Part of dbracket

Other Sublang

braces

histsub

History substitution uses !.

char-escapes

These backslash escape sequences are used in echo -e, printf, and in C-style strings like $'foo\n':

\\         backslash
\a         alert (BEL)
\b         backspace
\c         stop processing remaining input
\e         the escape character \x1b
\f         form feed
\n         newline
\r         carriage return
\t         tab
\v         vertical tab
\xHH       the byte with value HH, in hexadecimal
\uHHHH     the unicode char with value HHHH, in hexadecimal
\UHHHHHHHH the unicode char with value HHHHHHHH, in hexadecimal

Also:

\"         Double quote.

Inconsistent octal escapes:

\0NNN      echo -e '\0123'
\NNN       printf '\123'
           echo $'\123'

TODO: Verify other differences between echo -e, printf, and $''. See frontend/lexer_def.py.