z/OS V1R9.0 UNIX System Services Command ... - Christian Grothoff

sh
Quoting
found only in FPATH, this file will be read and executed in the current shell
environment (defining the functions contained in the file). The shell will then
execute the function matching the command name. This allows users to use
FPATH for locating functions without the need to identify every function with the
autoload command.
If FPATH is not set, or the command is not found in FPATH, the shell executes
the first matching file found in the PATH directories.
Command names can be marked as tracked aliases.The first time you run a
command with a tracked alias, the shell does a normal PATH search. If the search
is successful, the shell remembers the file that it finds. The next time you run a
command with the same name, sh immediately runs the file found on the last PATH
search; there is no new search. This speeds up the time that it takes the shell to
find the appropriate file.
The set –h command tells the shell that all commands should be treated as tracked
aliases. See alias and set for more information.
To let you override the special meaning of certain words or special characters, the
shell provides several quoting mechanisms. In general, you can turn off the special
meaning of any character by putting a backslash (\) in front of the character. This is
called escaping the character.
For example, you can tell the shell to disregard the special meaning of the newline
character by putting a backslash at the very end of a line. The shell ignores the
escaped newline, and joins the next line of input to the end of the current line. In
this way, you can enter long lines in a convenient and readable fashion.
Escaping characters by putting a backslash in front of them is the most direct way
of telling the shell to disregard special meanings. However, it can be awkward and
confusing if you have several characters to escape.
As an alternative, you can put arguments in various types of quotes. Different quote
characters have different “strengths.” The single-quote characters are the strongest.
When you enclose a command-line argument in single-quote characters, the shell
disregards the special meanings of everything inside the single quotes. For
example:
echo
’*’
Double-quote characters are weaker. Inside double quotes, the shell performs
command substitutions (see “Command Substitution” on page 563), parameter
substitutions (see “Parameter Substitution” on page 559) and arithmetic
substitutions (see “Arithmetic Substitution” on page 562). The shell does not
perform such substitutions when they appear inside single quotes. You can use the
backslash to escape another character when they appear inside double quotes, but
inside single quotes the shell ignores this special meaning.
The shell treats internal field separator characters (that is, characters in the value of
the IFS variable) literally inside quoted arguments, whether they’re quoted with
double quotes or single quotes. This means that a quoted argument is considered a
single entity, even if it contains IFS characters.
558 z/OS V1R9.0 UNIX System Services Command Reference