open(...)
public
Creates an IO object connected to the given
stream, file, or subprocess.
If path does not start with a pipe character
(``|’’), treat it as the name of a file to open using the specified mode (defaulting to
``r''). (See the table of valid modes on page 331.) If a file is
being created, its initial permissions may be set using the integer third
parameter.
If a block is specified, it will be invoked with the File object as a parameter, and the file will be
automatically closed when the block terminates. The call returns the value
of the block.
If path starts with a pipe character, a subprocess is created,
connected to the caller by a pair of
pipes. The returned IO object may be used
to write to the standard input and read from the standard output of this
subprocess. If the command following the ``|’’ is a
single minus sign, Ruby forks, and this subprocess is connected to the
parent. In the subprocess, the open call returns nil. If the
command is not ``-’’, the subprocess runs the command.
If a block is associated with an open("|-") call, that
block will be run twice—once in the parent and once in the child. The
block parameter will be an IO object in the
parent and nil in the child. The parent’s IO object will be connected to the child’s
$stdin and $stdout. The subprocess will be terminated at
the end of the block.
open("testfile") do |f|
print f.gets
end
produces:
This is line one
Open a subprocess and read its output:
cmd = open("|date")
print cmd.gets
cmd.close
produces:
Wed Apr 9 08:56:31 CDT 2003
Open a subprocess running the same Ruby program:
f = open("|-", "w+")
if f == nil
puts "in Child"
exit
else
puts "Got: #{f.gets}"
end
produces:
Got: in Child
Open a subprocess using a block to receive the I/O object:
open("|-") do |f|
if f == nil
puts "in Child"
else
puts "Got: #{f.gets}"
end
end
produces:
Got: in Child
Show source
/*
* call-seq:
* open(path [, mode [, perm]] ) => io or nil
* open(path [, mode [, perm]] ) {|io| block } => obj
*
* Creates an <code>IO</code> object connected to the given stream,
* file, or subprocess.
*
* If <i>path</i> does not start with a pipe character
* (``<code>|</code>''), treat it as the name of a file to open using
* the specified mode (defaulting to ``<code>r</code>''). (See the table
* of valid modes on page 331.) If a file is being created, its initial
* permissions may be set using the integer third parameter.
*
* If a block is specified, it will be invoked with the
* <code>File</code> object as a parameter, and the file will be
* automatically closed when the block terminates. The call
* returns the value of the block.
*
* If <i>path</i> starts with a pipe character, a subprocess is
* created, connected to the caller by a pair of pipes. The returned
* <code>IO</code> object may be used to write to the standard input
* and read from the standard output of this subprocess. If the command
* following the ``<code>|</code>'' is a single minus sign, Ruby forks,
* and this subprocess is connected to the parent. In the subprocess,
* the <code>open</code> call returns <code>nil</code>. If the command
* is not ``<code>-</code>'', the subprocess runs the command. If a
* block is associated with an <code>open("|-")</code> call, that block
* will be run twice---once in the parent and once in the child. The
* block parameter will be an <code>IO</code> object in the parent and
* <code>nil</code> in the child. The parent's <code>IO</code> object
* will be connected to the child's <code>$stdin</code> and
* <code>$stdout</code>. The subprocess will be terminated at the end
* of the block.
*
* open("testfile") do |f|
* print f.gets
* end
*
* <em>produces:</em>
*
* This is line one
*
* Open a subprocess and read its output:
*
* cmd = open("|date")
* print cmd.gets
* cmd.close
*
* <em>produces:</em>
*
* Wed Apr 9 08:56:31 CDT 2003
*
* Open a subprocess running the same Ruby program:
*
* f = open("|-", "w+")
* if f == nil
* puts "in Child"
* exit
* else
* puts "Got: #{f.gets}"
* end
*
* <em>produces:</em>
*
* Got: in Child
*
* Open a subprocess using a block to receive the I/O object:
*
* open("|-") do |f|
* if f == nil
* puts "in Child"
* else
* puts "Got: #{f.gets}"
* end
* end
*
* <em>produces:</em>
*
* Got: in Child
*/
static VALUE
rb_f_open(argc, argv)
int argc;
VALUE *argv;
{
if (argc >= 1) {
char *str = StringValuePtr(argv[0]);
if (str[0] == '|') {
VALUE tmp = rb_str_new(str+1, RSTRING(argv[0])->len-1);
OBJ_INFECT(tmp, argv[0]);
argv[0] = tmp;
return rb_io_s_popen(argc, argv, rb_cIO);
}
}
return rb_io_s_open(argc, argv, rb_cFile);
}