C++ system calls

Gil

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

In this case, I will probably be making unix calls like
'df' or 'statvfs' to get the diskspace information and
redirecting it to a file, and then opening and reading
the output.
Gil

Jul 22 '05 #1

Alf P. Steinbach

* br**************@hotmail.com (Gil) schriebt:

Is 'system' in stdlib.h the only way to make OS calls
from C++?
In one sense yes, namely that the standard library is defined
without reference to any particular OS, and that the language
does not directly support OS calls.

In another sense no, namely that 'system' as well as the i/o
facilities in the C and C++ standard libraries in practice uses
OS calls when suitable OS calls are available; they can be
regarded as abstractions over the OS, whatever the OS is.

In a third sense, the OS is probably mostly implemented in C
and/or C++, and a system-specific compiler (as most compilers
are...) will provide some system-specific means of making OS
API calls.


In this case, I will probably be making unix calls like
'df' or 'statvfs' to get the diskspace information and
redirecting it to a file, and then opening and reading
the output.

How to do that is off-topic in this group, but generally, you just
include the relevant headers and link with the appropriate libs.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Jul 22 '05 #2

Alf P. Steinbach

* br**************@hotmail.com (Gil) schriebt:

Is 'system' in stdlib.h the only way to make OS calls
from C++?
In one sense yes, namely that the standard library is defined
without reference to any particular OS, and that the language
does not directly support OS calls.

In another sense no, namely that 'system' as well as the i/o
facilities in the C and C++ standard libraries in practice uses
OS calls when suitable OS calls are available; they can be
regarded as abstractions over the OS, whatever the OS is.

In a third sense, the OS is probably mostly implemented in C
and/or C++, and a system-specific compiler (as most compilers
are...) will provide some system-specific means of making OS
API calls.


In this case, I will probably be making unix calls like
'df' or 'statvfs' to get the diskspace information and
redirecting it to a file, and then opening and reading
the output.

How to do that is off-topic in this group, but generally, you just
include the relevant headers and link with the appropriate libs.

--
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing on usenet and in e-mail?

Jul 22 '05 #3

Saikrishna

There are definetly file system related calls in C/C++ like
statfs,fstatfs that gives you information about a mounted file
system. ( Total Number of Blocks allocated, free blocks, block size..etc).
I have worked with these in Linux but never tried in Solaris.

-Sai

br**************@hotmail.com (Gil) wrote in message news:<ad**************************@posting.google. com>...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

In this case, I will probably be making unix calls like
'df' or 'statvfs' to get the diskspace information and
redirecting it to a file, and then opening and reading
the output.
Gil

Jul 22 '05 #4

Saikrishna

There are definetly file system related calls in C/C++ like
statfs,fstatfs that gives you information about a mounted file
system. ( Total Number of Blocks allocated, free blocks, block size..etc).
I have worked with these in Linux but never tried in Solaris.

-Sai

br**************@hotmail.com (Gil) wrote in message news:<ad**************************@posting.google. com>...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

In this case, I will probably be making unix calls like
'df' or 'statvfs' to get the diskspace information and
redirecting it to a file, and then opening and reading
the output.
Gil

Jul 22 '05 #5

Thomas Matthews

Saikrishna wrote:

br**************@hotmail.com (Gil) wrote in message news:<ad**************************@posting.google. com>...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

In this case, I will probably be making unix calls like
'df' or 'statvfs' to get the diskspace information and
redirecting it to a file, and then opening and reading
the output.
Gil There are definetly file system related calls in C/C++ like
statfs,fstatfs that gives you information about a mounted file
system. ( Total Number of Blocks allocated, free blocks, block

size..etc). I have worked with these in Linux but never tried in Solaris.

-Sai

1. Its Annoying.
2. So don't Top-Post. Replies are either interspersed
or appended to the bottom, like this one.

By the way, statfs, fstatfs are not standard calls in
either C or C++. And yes, they are two different
languages. There is not one language called C/C++.

If you believe the above are _standard_ functions,
please correct me by quoting the ISO/ANSI specification.
--
Thomas Matthews

C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
C++ Faq: http://www.parashift.com/c++-faq-lite
C Faq: http://www.eskimo.com/~scs/c-faq/top.html
alt.comp.lang.learn.c-c++ faq:
http://www.raos.demon.uk/acllc-c++/faq.html
Other sites:
http://www.josuttis.com -- C++ STL Library book

Jul 22 '05 #6

Thomas Matthews

Saikrishna wrote:

br**************@hotmail.com (Gil) wrote in message news:<ad**************************@posting.google. com>...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

In this case, I will probably be making unix calls like
'df' or 'statvfs' to get the diskspace information and
redirecting it to a file, and then opening and reading
the output.
Gil There are definetly file system related calls in C/C++ like
statfs,fstatfs that gives you information about a mounted file
system. ( Total Number of Blocks allocated, free blocks, block

size..etc). I have worked with these in Linux but never tried in Solaris.

-Sai

1. Its Annoying.
2. So don't Top-Post. Replies are either interspersed
or appended to the bottom, like this one.

By the way, statfs, fstatfs are not standard calls in
either C or C++. And yes, they are two different
languages. There is not one language called C/C++.

If you believe the above are _standard_ functions,
please correct me by quoting the ISO/ANSI specification.
--
Thomas Matthews

C++ newsgroup welcome message:
http://www.slack.net/~shiva/welcome.txt
C++ Faq: http://www.parashift.com/c++-faq-lite
C Faq: http://www.eskimo.com/~scs/c-faq/top.html
alt.comp.lang.learn.c-c++ faq:
http://www.raos.demon.uk/acllc-c++/faq.html
Other sites:
http://www.josuttis.com -- C++ STL Library book

Jul 22 '05 #7

Nick Hounsome

"Gil" <br**************@hotmail.com> wrote in message
news:ad**************************@posting.google.c om...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

No - I think you will find that popen is std C and more directly useful than
system
because it gives you a FILE* to pipe in teh result.

The actual progs are OS specific and hence not C++ but I think you will
find that there are API calls.

RTFM :-)

Jul 22 '05 #8

Nick Hounsome

"Gil" <br**************@hotmail.com> wrote in message
news:ad**************************@posting.google.c om...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

No - I think you will find that popen is std C and more directly useful than
system
because it gives you a FILE* to pipe in teh result.

The actual progs are OS specific and hence not C++ but I think you will
find that there are API calls.

RTFM :-)

Jul 22 '05 #9

Kevin Goodsell

Nick Hounsome wrote:

"Gil" <br**************@hotmail.com> wrote in message
news:ad**************************@posting.google.c om...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

No - I think you will find that popen is std C and more directly useful than
system
because it gives you a FILE* to pipe in teh result.

No, he will not find that popen() is standard C. It's not. Nor is it
standard C++.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

Jul 22 '05 #10

Kevin Goodsell

Nick Hounsome wrote:

"Gil" <br**************@hotmail.com> wrote in message
news:ad**************************@posting.google.c om...

I am running a C++ process on Solaris that needs
to find out how much diskspace is free and used on
the system.

Is 'system' in stdlib.h the only way to make OS calls
from C++?

No - I think you will find that popen is std C and more directly useful than
system
because it gives you a FILE* to pipe in teh result.

No, he will not find that popen() is standard C. It's not. Nor is it
standard C++.

-Kevin
--
My email address is valid, but changes periodically.
To contact me please use the address from a recent posting.

Jul 22 '05 #11

Christopher Benson-Manica

Gil <br**************@hotmail.com> spoke thus:

<point granularity="fine" confidence="7/10">

Is 'system' in stdlib.h the only way to make OS calls
from C++?

system() does not allow you to make "OS calls". What it does
do is pass a command string to a shell or other command
interpreter (DOS, bash, ksh, whatever), which may or may not
issue system calls to handle the command. If you wish to issue
the system calls yourself (your next paragraph suggests that you
do), you must employ implementation-specific extensions to C/C++
which are, as others have noted, not to be discussed here.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cyberspace.org | don't, I need to know. Flames welcome.

Jul 22 '05 #12

Christopher Benson-Manica

Gil <br**************@hotmail.com> spoke thus:

<point granularity="fine" confidence="7/10">

Is 'system' in stdlib.h the only way to make OS calls
from C++?

system() does not allow you to make "OS calls". What it does
do is pass a command string to a shell or other command
interpreter (DOS, bash, ksh, whatever), which may or may not
issue system calls to handle the command. If you wish to issue
the system calls yourself (your next paragraph suggests that you
do), you must employ implementation-specific extensions to C/C++
which are, as others have noted, not to be discussed here.

--
Christopher Benson-Manica | I *should* know what I'm talking about - if I
ataru(at)cyberspace.org | don't, I need to know. Flames welcome.

Jul 22 '05 #13