FBB::CerrExtractor(3bobcat)
Executing Child Processes
(libbobcat-dev_6.06.02)
2005-2024
NAME
FBB::CerrExtractor - Runs external programs writing standard error
SYNOPSIS
    #include <bobcat/cerrextractor>
    Linking option: -lbobcat
DESCRIPTION
    The FBB::CerrExtractor class offers a basic interface for calling
external programs (so-called child processes) writing their standard error
streams. The standard input and standard output streams of the child processes
are by default not handled by CerrExtractor objects. The child's standard
error is read through the CerrExtractor object: information written by the
child process to its standard error stream is extracted or read from
CerrExtractor object. The PATH environment variable is not used when
calling child processes: child process programs must be specified using paths.
CerrExtractor 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
    -  CerrExtractor(size_t bufSize = 100):
 A bufSize argument may be specified: it defines the internal
        buffer size used by the CerrExtractor's streambuf. By default the
        standard input and standard output streams are not handled.
 
-  CerrExtractor(Mode mode, size_t bufSize = 100):
 The mode argument must be CerrExtractor::CLOSE_STD. It
        indicates that the standard input and standard error streams are
        redirected to /dev/null: the child processes cannot read their
        standard input streams and any standard output generated by child
        processes is ignored. 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 using an absolute path (the PATH environment variable
        isn't used).  This member immediately returns, after which information
        written by the child process to its standard error stream may be
        extracted from the CerrExtractor 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), cininserter(3bobcat), coutextractor(3bobcat),
    execl(3), exec(3bobcat),
    fork(3bobcat), process(3bobcat), stdextractor(3bobcat).
BUGS
    None reported.
BOBCAT PROJECT FILES
    -  https://fbb-git.gitlab.io/bobcat/: gitlab project page;
    
-  bobcat_6.06.02-x.dsc: detached signature;
    
-  bobcat_6.06.02-x.tar.gz: source archive;
    
-  bobcat_6.06.02-x_i386.changes: change log;
    
-  libbobcat1_6.06.02-x_*.deb: debian package containing the
            libraries;
    
-  libbobcat1-dev_6.06.02-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).