18 The SYSTEM Package

open-pipe

Function

Package

system

Syntax

open-pipe command &key {keyword value}* => stream

The valid keyword/value pairs are:

:direction {:input|:output|:io}

:element-type element-type

:interrupt-off {t|nil}

:shell-type

Arguments

command: A string
direction: A keyword. Either:input or:io.
element-type: A symbol.
interrupt-off: A boolean.
shell-type: A shell type.

Values

stream: A file stream.

Description

The behaviour ofopen-pipe is analogous to that ofpopen in the UNIX library. It creates a unidirectional pipe to/from a subprocess and returns a stream. The stream can be read from or written to as appropriate.

The command argument passes a shell command as a string.

direction is a keyword for the stream direction. The default value is:input. Bidirectional (i/o) pipes may be created by setting this keyword to:io. See the example below.

element-type specifies the type of the stream as withopen. The default value isstring-char.

interrupt-off, ift, ensures that Ctrl+C (SIGINT) to the LispWorks image is ignored by the subprocess.

shell-type specifies the type of UNIX shell to run.

Examples

SYSTEM 106 > (setq s (open-pipe "ls"))

#<Pipe stream "ls">

SYSTEM 107 > (read-line s)

"#draw-string.lisp#"
NIL

SYSTEM 108 > (read-line s)

"#drawing-state.lisp#"
NIL

SYSTEM 109 >

: The following example shows you how to use bidirectional pipes.

SYSTEM 17 > (with-open-stream
                (s (open-pipe "/bin/csh"
                             :direction :io
                             :buffered nil))
                (write-line "whoami" s)
                (read-line s))
"andrews@arrakis [users/andrews]> andrews"
NIL

SYSTEM 18 >

See also
: call-system
call-system-showing-output