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

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and this second shell actually runs command. In this way, command runs in
a completely separate execution environment; it can change working
directories, change variables, open files, and so on without affecting the first
shell. The child shell’s environment begins as a copy of the current
environment, so the value of the ENV environment variable is not run when
achild shell starts.
| Creates a pipe between the two commands that the | operator
connects.The standard output is the first command becomes the standard
input of the second command. A series of commands connected by pipes is
called a pipeline.The exit status is that of the last command in the pipeline.
&& Is the logical AND operator. The shell runs the second command if and only
if the first command returns a true (zero) exit status.
|| This is the logical OR operator. The shell runs the second command if and
only if the first command returns a false (nonzero) exit status.
& Runs the command that precedes it asynchronously. The shell just starts
the command running and then immediately goes on take new input, before
the command finishes execution. On systems where asynchronous
execution is not possible, this operation is effectively equivalent to ;.
|& Runs the command that precedes it as a co-process.The command runs
asynchronously, as with the & operator, but the command’s standard input
and standard output are connected to the shell by pipes. The shell sends
input to command’s standard input with the print –p command, and reads
from command’s standard output with the read –p command. The
command should not buffer its output. Because of this and other limitations,
co-processes should be designed to be used as co-processes. On systems
where asynchronous execution is not possible, co-processes are not
supported.
; Is the sequential execution operator. The second command is run only after
the first command has completed.
newline
The unescaped newline is equivalent to the ; operator.
Reserved-Word Commands
The shell contains a rich set of reserved-word commands, which provide flow of
control and let you create compound commands. In the following list, a command
can also be a sequence of commands separated by newlines. Square brackets ([ ])
indicate optional portions of commands, and are included as part of the command
syntax except in the case of [[ test_expr ]], where square brackets are part of the
command.
! The exclamation point is the logical NOT command. When its operand is
false (nonzero), this command returns true (zero). When its operand is true
(zero), this command returns false (nonzero).
{command;}
Enclosing a command in braces is similar to the (command) construct,
except that the shell runs the command in the same environment rather
than under a child shell. { and } are reserved words to the shell. To make it
possible for the shell to recognize these symbols, you must put a blank or
newline after the {, and a semicolon or newline before the }.
552 z/OS V1R9.0 UNIX System Services Command Reference