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<concept xml:lang="en" id="GUID-8F6D6934-8FF0-5045-8AB1-74384BE792EA"><title>Retrieving Information about a Shared Memory Object</title><prolog><metadata><keywords/></metadata></prolog><conbody><p>You can use the <xref href="GUID-7A657C7B-0732-322C-8378-5230305EE59E.dita"><apiname>fstat()</apiname></xref> function to retrieve information about a shared memory object associated with a file descriptor. The <xref href="GUID-7A657C7B-0732-322C-8378-5230305EE59E.dita"><apiname>fstat()</apiname></xref> function retrieves only the following members associated with a shared memory from the structure <codeph>stat</codeph> declared in <filepath>&lt;sys/stat.h&gt;</filepath>: </p> <ul><li id="GUID-8458BD50-D542-59B0-93B5-2B7604D04D98"><p> <codeph> st_uid</codeph>  </p> </li> <li id="GUID-6E5438E5-4643-538D-9287-EB80525687AF"><p> <codeph> st_gid</codeph>  </p> </li> <li id="GUID-F91DAE1E-FBE6-5B0B-8B20-0970418FE24F"><p> <codeph>st_size</codeph>  </p> </li> <li id="GUID-42822FB5-C7F0-55A4-822C-A23BB6223100"><p> <codeph>st_mode</codeph>  </p> </li> </ul> <p>For more information about the members of the structure <codeph>stat</codeph>, see <xref scope="external" href="http://www.opengroup.org/onlinepubs/009695399/basedefs/sys/stat.h.html">Open Group</xref>  </p> <p>Example: </p> <codeblock id="GUID-4AEA7CD0-3944-557D-A3D1-D802B318E5FC" xml:space="preserve">#include &lt;stdio.h&gt;

#include <sys/mman.h>

#include <fcntl.h>

#include <sys/stat.h>

#include <errno.h>

int main(void)

    {

    int fd; //File descriptor

    int ret;

    struct stat buffer; //Stores the data associated with the members of the structure stat

    if((fd = shm_open("page", O_RDWR|O_CREAT, 0666)) < 0)

        {

        printf("Shared memory creation failed with errno %d\n", errno);

        }

    else

        {

        printf("Shared memory creation was successful\n");

        }

    if((ret = fstat(fd,&buffer) < 0)

        {

        printf("fstat() on shared memory failed with errno %d\n", errno);

        }

    else

        {

        printf("fstat() on shared memory succeeded\n");

        printf("mode = %d\n", buffer.st_mode);

        printf("size = %d\n", buffer.st_size);

        }

    //Checks whether the shared memory mode is same as that of a regular file

    if(S_ISREG(buffer.st_mode))

        {

        printf("Test passed");

        }

    else

        {

        printf("Test failed");

        }

    close(fd);//closing the file descriptor

    if((ret = shm_unlink("page")) < 0) 

        {

        printf("Shared memory unlinking failed with errno %d\n", errno);

        }

    else

        {

        printf("Shared memory unlinking was successful\n");

        }

    return ret;

    }</codeblock> </conbody><related-links><link href="GUID-9AC6774A-41E9-5298-8696-0A317A09E1E9.dita"><linktext>Librt Overview</linktext> </link> <link href="GUID-BE70DCBF-366A-5054-B0F1-7FCEF45FC735.dita"><linktext>Creating and Unlinking a File

                Descriptor from a Shared Memory</linktext> </link> <link href="GUID-A4ECB450-02DA-5E85-91AC-4C8BDE0B9B58.dita"><linktext>Writing, Reading and Seeking from a

                Shared Memory</linktext> </link> <link href="GUID-66402932-5C44-556B-A7AC-1C2D245C8B05.dita"><linktext>Clocks and Timers Tutorial</linktext> </link> </related-links></concept>