diff options
Diffstat (limited to 'man3/shm_open.3')
| -rw-r--r-- | man3/shm_open.3 | 35 |
1 files changed, 17 insertions, 18 deletions
diff --git a/man3/shm_open.3 b/man3/shm_open.3 index c5756c4..6d07292 100644 --- a/man3/shm_open.3 +++ b/man3/shm_open.3 @@ -3,7 +3,7 @@ .\" .\" SPDX-License-Identifier: Linux-man-pages-copyleft .\" -.TH shm_open 3 2023-07-20 "Linux man-pages 6.05.01" +.TH shm_open 3 2023-10-31 "Linux man-pages 6.7" .SH NAME shm_open, shm_unlink \- create/open or unlink POSIX shared memory objects .SH LIBRARY @@ -14,7 +14,7 @@ Real-time library .B #include <sys/mman.h> .BR "#include <sys/stat.h>" " /* For mode constants */" .BR "#include <fcntl.h>" " /* For O_* constants */" -.PP +.P .BI "int shm_open(const char *" name ", int " oflag ", mode_t " mode ); .BI "int shm_unlink(const char *" name ); .fi @@ -30,7 +30,7 @@ The function performs the converse operation, removing an object previously created by .BR shm_open (). -.PP +.P The operation of .BR shm_open () is analogous to that of @@ -51,7 +51,7 @@ followed by one or more characters, none of which are slashes. .\" case the subdirectory must exist under /dev/shm, and allow the .\" required permissions if a user wants to create a shared memory .\" object in that subdirectory. -.PP +.P .I oflag is a bit mask created by ORing together exactly one of .B O_RDONLY @@ -107,10 +107,10 @@ does not exist, are performed atomically. .TP .B O_TRUNC If the shared memory object already exists, truncate it to zero bytes. -.PP +.P Definitions of these flag values can be obtained by including .IR <fcntl.h> . -.PP +.P On successful completion .BR shm_open () returns a new file descriptor referring to the shared memory object. @@ -121,7 +121,7 @@ The flag (see .BR fcntl (2)) is set for the file descriptor. -.PP +.P The file descriptor is normally used in subsequent calls to .BR ftruncate (2) @@ -130,7 +130,7 @@ to After a call to .BR mmap (2) the file descriptor may be closed without affecting the memory mapping. -.PP +.P The operation of .BR shm_unlink () @@ -235,7 +235,6 @@ T{ .BR shm_unlink () T} Thread safety MT-Safe locale .TE -.sp 1 .SH VERSIONS POSIX leaves the behavior of the combination of .B O_RDONLY @@ -244,7 +243,7 @@ and unspecified. On Linux, this will successfully truncate an existing shared memory object\[em]this may not be so on other UNIX systems. -.PP +.P The POSIX shared memory object implementation on Linux makes use of a dedicated .BR tmpfs (5) @@ -255,7 +254,7 @@ POSIX.1-2008. .SH HISTORY glibc 2.2. POSIX.1-2001. -.PP +.P POSIX.1-2001 says that the group ownership of a newly created shared memory object is set to either the calling process's effective group ID or "a system default group ID". @@ -271,7 +270,7 @@ of a string that is placed into the shared memory by the "send" program. Once the data has been modified, the "send" program then prints the contents of the modified shared memory. An example execution of the two programs is the following: -.PP +.P .in +4n .EX $ \fB./pshm_ucase_bounce /myshm &\fP @@ -280,14 +279,14 @@ $ \fB./pshm_ucase_send /myshm hello\fP HELLO .EE .in -.PP +.P Further detail about these programs is provided below. .\" .SS Program source: pshm_ucase.h The following header file is included by both programs below. Its primary purpose is to define a structure that will be imposed on the memory object that is shared between the two programs. -.PP +.P .in +4n .\" SRC BEGIN (pshm_ucase.h) .EX @@ -325,12 +324,12 @@ match the size of the structure defined in the header file. It then maps the object into the process's address space, and initializes two POSIX semaphores inside the object to 0. -.PP +.P After the "send" program has posted the first of the semaphores, the "bounce" program upper cases the data that has been placed in the memory by the "send" program and then posts the second semaphore to tell the "send" program that it may now access the shared memory. -.PP +.P .in +4n .\" SRC BEGIN (pshm_ucase_bounce.c) .EX @@ -413,7 +412,7 @@ main(int argc, char *argv[]) The "send" program takes two command-line arguments: the pathname of a shared memory object previously created by the "bounce" program and a string that is to be copied into that object. -.PP +.P The program opens the shared memory object and maps the object into its address space. It then copies the data specified in its second argument @@ -423,7 +422,7 @@ which tells the "bounce" program that it can now access that data. After the "bounce" program posts the second semaphore, the "send" program prints the contents of the shared memory on standard output. -.PP +.P .in +4n .\" SRC BEGIN (pshm_ucase_send.c) .EX |