Parameters

command-sequence

   A DCL command, a pipeline, or a subshell:

   o  DCL command

      A DCL command string, which can include qualifiers,
      parameters, keywords, and values.

   o  Pipeline

      A pipeline is a sequence of pipeline-segment commands
      connected by pipes, represented by the vertical-bar (|)
      separator. A pipeline-segment command is a DCL command that
      appears in a pipeline. The pipe connects the SYS$OUTPUT of one
      pipeline-segment command to the SYS$INPUT of the next command.
      The format of a pipeline is as follows:

      pipeline-segment-command | pipeline-segment-command [|...]

   o  Subshell

      A subshell is one or more command sequences separated by
      separators and enclosed in parentheses. The format of a
      subshell is as follows:

      (command-sequence [separator command-sequence]...)

   Input/output redirection is allowed in a command sequence. The
   command before an angle bracket (> or <) redefines its SYS$INPUT,
   SYS$OUTPUT, or SYS$ERROR during execution. You cannot use angle
   brackets (<>) to represent a directory specification in a PIPE
   command because the PIPE command interprets angle brackets as
   input/output redirection syntax.


separator

   Determines the processing action of the command sequences
   specified in a PIPE command. The valid PIPE separators are
   described in the following table.


   Separator  Action

   |          Key pipe separator. The pipe connects the SYS$OUTPUT of
              one pipeline-segment command to the SYS$INPUT of the
              next command.
   ;          Sequential execution. The command sequence following
              the semicolon (;) is executed after the preceding
              command sequence is completed. You must precede
              this separator with a blank space; otherwise, it is
              parsed as the Record Management System (RMS) file
              specification version number delimiter.
   &&         Conditional execution (upon success). The command
              sequence following the double ampersand (&&) is
              executed only if the preceding command sequence
              succeeds.
   ||         Conditional execution (upon failure). The command
              sequence following the double vertical bar (||) is
              executed only if the preceding command sequence fails.
   &          Background execution. All command sequences that
              precede the ampersand (&) are executed asynchronously
              in a subprocess environment. The & separator is similar
              to the SPAWN/NOWAIT command.

              Note: Any ampersand that precedes a character string
              without spaces in between is parsed as a conventional
              DCL symbol substitution expression rather than the
              background execution syntax.
   @TEE       Command file, TEE.COM. Used for redirecting output to
              two targets (for example, one output is directed to
              the next stage in pipeline, and the other to a file).
              See the Examples section for an example of how to use
              TEE.COM.

   In a PIPE command line, the "&" has the highest precedence,
   followed by "|", ";", "&&", and "||", which have equal
   precedence.