Qshell Interpreter (qsh) - FTP Directory Listing - IBM

$(command)
or by using backquotes:
′command′
Arithmetic expansion
Field splitting
The backquoted version is provided for compatibility and its use is discouraged.
The shell expands the command substitution by running command in a subshell
environment and replacing the command substitution with the standard output of the
command, removing sequences of one or more s at the end of the
substitution. Embedded s before the end of the output are not removed;
however, during field splitting, they may be translated into s, depending on
the value of the IFS variable and quoting that is in effect.
Arithmetic expansion provides a mechanism for evaluating an arithmetic expression
and substituting its value. The format for arithmetic expansion is:
$((expression))
Path name expansion
Quote removal
18 Qshell Interpreter (qsh)
The expression is treated as if it were in double-quotes, except that a double-quote
inside expression is not treated specially. The shell expands all tokens in expression
for parameter expansion, command substitution, and quote removal. qsh treats the
result as an arithmetic expression (page 19) and substitutes the value of the
expression.
After parameter expansion, command substitution, and arithmetic expansion qsh
scans the results of expansions and substitutions that did not occur in
double-quotes for field splitting and multiple fields can result.
qsh treats each character of the IFS variable as a delimiter and uses the delimiters
to split the results of parameter expansion and command substitution into fields. If
the value of the IFS variable is null, no field splitting is performed.
When the noglob option is not set, file name generation is performed after field
splitting is complete. Each word is viewed as a series of patterns (page 18),
separated by slashes. The process of expansion replaces the word with the names
of all existing files whose names can be formed by replacing each pattern with a
string that matches the specified pattern. There are two restrictions:
1. a pattern cannot match a string containing a slash, and
2. a pattern cannot match a string starting with a period unless the first character
of the pattern is a period.
The quote characters, backslash (\), single quote (′), and double quote (“), are
removed unless the character has been quoted.