FBB::StdExtractor(3bobcat)
Executing Child Processes
(libbobcat-dev_6.04.00)
2005-2023
NAME
FBB::StdExtractor - Runs external programs writing standard error
SYNOPSIS
#include <bobcat/cerrextractor>
Linking option: -lbobcat
DESCRIPTION
The FBB::StdExtractor class offers a basic interface for calling
external programs (so-called child processes) writing their standard
output and error streams. The standard input stream of the child processes are
by default not handled by StdExtractor objects. The child's standard
output and standard error streams are read through the StdExtractor
object: information written by the child process to these streams is extracted
or read from StdExtractor object. The PATH environment variable is not
used when calling child processes: child process programs must be specified
using paths.
StdExtractor objects may repeatedly be used to execute the same or
different child processes.
Arguments passed to child processes may be surrounded by double or single
quotes. Arguments surrounded by double quotes have their double quotes
removed, while interpreting any escape-sequences that may have been used
within. Arguments surrounded by single quotes have their single quotes
removed, while accepting their content as-is. In addition unquoted
escape-sequences may be specified: those escape sequences are evaluated and
replaced by their intended characters (e.g., \100 is converted to @).
NAMESPACE
FBB
All constructors, members, operators and manipulators, mentioned in this
man-page, are defined in the namespace FBB.
INHERITS FROM
FBB::Exec (private),
FBB::IFdBuf (private),
std::istream
CONSTRUCTOR
- StdExtractor(size_t bufSize = 100):
A bufSize argument may be specified: it defines the internal
buffer size used by the StdExtractor's streambuf. By default the
stdandard input stream is not handled.
- CoutExtractor(Mode mode, size_t bufSize = 100):
The mode argument must be StdExtractor::CLOSE_STD. It indicates
that the standard input stream is redirected to /dev/null: the
child processes cannot read their standard input streams. A
bufSize argument may be specified: it defines the internal buffer
size used by the CinInserter's streambuf.
Copy and move constructors (and assignment operators) are not available.
MEMBERS
- void execute(std::string const &cmd):
The argument specifies the command to execute: the command itself must
be specified as a path (the PATH environment variable isn't
used). This member immediately returns, after which information
written by the child process to its standard output and standard error
streams may be extracted from the StdExtractor object.
Once execute has returned it can be called again, either using the
same or another command.
Arguments passed to the program to be executed as child process may
optionally be specified using single or double quotes, as described in
this man-page's DESCRIPTION section.
- int ret() const:
Once execute has returned this member provides the actual exit code
of the child process. Its value equals -1 before the first exectue
call.
PROTECTED MEMBER
- Pipe &childOutPipe():
If derived classes need to override the redirections-members then they
probabaly need access to the pipe written by the child process. This
member provides a reference to that pipe. By default the parent
process reads information from the pipe, while the child process
inserts its standard error output into the pipe.
EXAMPLE
#include <iostream>
#include <bobcat/cerrextractor>
using namespace std;
using namespace FBB;
int main()
{
CerrExtractor extractor;
extractor.execute("/bin/cat driver.cc");
cout << extractor.rdbuf();
cerr << "Returning: " << extractor.ret() << "\n"
"again:\n";
extractor.execute("/bin/cat driver.cc");
cout << extractor.rdbuf();
cerr << "Returning: " << extractor.ret() << '\n';
}
FILES
bobcat/cerrextractor - provides the class interface
SEE ALSO
bobcat(7), cerrextractor(3bobcat),
cininserter(3bobcat), coutextractor(3bobcat),
execl(3), exec(3bobcat),
fork(3bobcat), process(3bobcat).
BUGS
None reported.
BOBCAT PROJECT FILES
- https://fbb-git.gitlab.io/bobcat/: gitlab project page;
- bobcat_6.04.00-x.dsc: detached signature;
- bobcat_6.04.00-x.tar.gz: source archive;
- bobcat_6.04.00-x_i386.changes: change log;
- libbobcat1_6.04.00-x_*.deb: debian package containing the
libraries;
- libbobcat1-dev_6.04.00-x_*.deb: debian package containing the
libraries, headers and manual pages;
BOBCAT
Bobcat is an acronym of `Brokken's Own Base Classes And Templates'.
COPYRIGHT
This is free software, distributed under the terms of the
GNU General Public License (GPL).
AUTHOR
Frank B. Brokken (f.b.brokken@rug.nl).