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diff --git a/man2/intro.2 b/man2/intro.2 deleted file mode 100644 index 74af07c..0000000 --- a/man2/intro.2 +++ /dev/null @@ -1,115 +0,0 @@ -.\" Copyright (C) 2007 Michael Kerrisk <mtk.manpages@gmail.com> -.\" -.\" SPDX-License-Identifier: Linux-man-pages-copyleft -.\" -.\" 2007-10-23 mtk: moved the _syscallN specific material to the -.\" new _syscall(2) page, and substantially enhanced and rewrote -.\" the remaining material on this page. -.\" -.TH intro 2 2023-10-31 "Linux man-pages 6.7" -.SH NAME -intro \- introduction to system calls -.SH DESCRIPTION -Section 2 of the manual describes the Linux system calls. -A system call is an entry point into the Linux kernel. -Usually, system calls are not invoked directly: -instead, most system calls have corresponding C library -wrapper functions which perform the steps required -(e.g., trapping to kernel mode) in order to invoke -the system call. -Thus, making a system call looks the same as invoking a normal -library function. -.P -In many cases, the C library wrapper function does nothing more than: -.IP \[bu] 3 -copying arguments and the unique system call number to the -registers where the kernel expects them; -.IP \[bu] -trapping to kernel mode, -at which point the kernel does the real work of the system call; -.IP \[bu] -setting -.I errno -if the system call returns an error number when the kernel returns the -CPU to user mode. -.P -However, in a few cases, a wrapper function may do rather more than this, -for example, performing some preprocessing -of the arguments before trapping to kernel mode, -or postprocessing of values returned by the system call. -Where this is the case, the manual pages in Section 2 generally -try to note the details of both the (usually GNU) C library API -interface and the raw system call. -Most commonly, the main DESCRIPTION will focus on the C library interface, -and differences for the system call are covered in the NOTES section. -.P -For a list of the Linux system calls, see -.BR syscalls (2). -.SH RETURN VALUE -On error, most system calls return a negative error number -(i.e., the negated value of one of the constants described in -.BR errno (3)). -The C library wrapper hides this detail from the caller: when a -system call returns a negative value, the wrapper copies the -absolute value into the -.I errno -variable, and returns \-1 as the return value of the wrapper. -.P -The value returned by a successful system call depends on the call. -Many system calls return 0 on success, but some can return nonzero -values from a successful call. -The details are described in the individual manual pages. -.P -In some cases, -the programmer must define a feature test macro in order to obtain -the declaration of a system call from the header file specified -in the man page SYNOPSIS section. -(Where required, these feature test macros must be defined before including -.I any -header files.) -In such cases, the required macro is described in the man page. -For further information on feature test macros, see -.BR feature_test_macros (7). -.SH STANDARDS -Certain terms and abbreviations are used to indicate UNIX variants -and standards to which calls in this section conform. -See -.BR standards (7). -.SH NOTES -.SS Calling directly -In most cases, it is unnecessary to invoke a system call directly, -but there are times when the Standard C library does not implement -a nice wrapper function for you. -In this case, the programmer must manually invoke the system call using -.BR syscall (2). -Historically, this was also possible using one of the _syscall macros -described in -.BR _syscall (2). -.SS Authors and copyright conditions -Look at the header of the manual page source for the author(s) and copyright -conditions. -Note that these can be different from page to page! -.SH SEE ALSO -.ad l -.nh -.BR _syscall (2), -.BR syscall (2), -.BR syscalls (2), -.BR errno (3), -.BR intro (3), -.BR capabilities (7), -.BR credentials (7), -.BR feature_test_macros (7), -.BR mq_overview (7), -.BR path_resolution (7), -.BR pipe (7), -.BR pty (7), -.BR sem_overview (7), -.BR shm_overview (7), -.BR signal (7), -.BR socket (7), -.BR standards (7), -.BR symlink (7), -.BR system_data_types (7), -.BR sysvipc (7), -.BR time (7) |