/**
* slibc — Yet another C library
* Copyright © 2015 Mattias Andrée (maandree@member.fsf.org)
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef _UNISTD_H
#define _UNISTD_H
#include <slibc/version.h>
#include <slibc/features.h>
#define __NEED_size_t
#define __NEED_ssize_t
#define __NEED_uid_t
#define __NEED_gid_t
#define __NEED_off_t
#define __NEED_pid_t
#define __NEED_ptrdiff_t
#define __NEED_intptr_t
#define __NEED_useconds_t
#include <bits/types.h>
/**
* `NULL`'s canonical header is <stddef.h>.
*/
#ifndef NULL
# define NULL ((void*)0)
#endif
/**
* The file descriptor for stdin.
* The file with input.
*
* @etymology (St)andar(d) (in)put (file)descriptor (number).
*
* @since Always.
*/
#define STDIN_FILENO 0
/**
* The file descriptor for stdout.
* The file for output.
*
* @etymology (St)andar(d) (out)put (file)descriptor (number).
*
* @since Always.
*/
#define STDOUT_FILENO 1
/**
* The file descriptor for stderr.
* The file for error messages and warnings.
*
* @etymology (St)andar(d) (err)or output (file)descriptor (number).
*
* @since Always.
*/
#define STDERR_FILENO 2
/* TODO temporary values */
#define F_OK 0
#define X_OK 1
#define W_OK 2
#define R_OK 4
/**
* Set the high end of the calling process's
* data segment.
*
* The high end is defined as the last byte
* in the segment plus 1.
*
* Using `brk` is highly discouraged. `malloc`,
* `calloc` and `free`, and its related functions,
* fall be used instead as they are much more
* conformable. Use of `brk` can couse errors
* when using `malloc`, `free`, &c. Thus, `brk`
* shall (bascially) only be used if you are
* writting an alterantive malloc-implementation.
*
* `brk` was marked LEGACY in SUSv2, and it
* was removed from the POSIX standard in revision
* POSIX.1-2001. It is however fundamental in
* implementing a fast `malloc`-implementation.
*
* @etymology Set (br)ea(k).
*
* @param address The process's new high end of its data segment.
* If lower than the current low end, nothing will
* happen and the function will return with a success
* status.
* @return Zero on succes, -1 on error. On error, `errno`
* is set to indicate the error.
*
* @throws ENOMEM The process can allocate the requested amount
* of memory. Either the process store limit would
* have been exceeded, RAM and swap memory would
* have been exhausted, or the request would cause
* the data segment to overlap another segment.
*
* @since Always.
*/
int brk(void*) /* TODO implement brk */
__GCC_ONLY(__attribute__((__warn_unused_result__)));
/**
* Set and get the current high end of the calling
* process's data segment.
*
* There is some documents that state that the new,
* rather than the previous, high end is returned.
* Additionally, some documentions do not document
* possible failure. Thus only `sbrk(0)` is guaranteed
* to be portable. The return type differs between
* implementations; common return types are `int`,
* `ssize_t`, `ptrdiff_t`, `ptrdiff_t`, `intptr_t`,
* and `void*`. Note that `int` is
* microarchitecture-portable.
*
* `sbrk` was marked LEGACY in SUSv2, and it
* was removed from the POSIX standard in revision
* POSIX.1-2001. It is however fundamental in
* implementing a fast `malloc`-implementation.
*
* @etymology Shift (br)ea(k).
*
* @param delta The incremant of the size of the data segment,
* zero means that the high end shall not be moved
* (thus the current high end is returned,) a
* positive value will cause the segment to grow,
* a negative value will cause the segment to shrink.
* @return The previous high end. `(void*)-1` is returned on error.
*
* @throws ENOMEM The process can allocate the requested amount
* of memory. Either the process store limit would
* have been exceeded, RAM and swap memory would
* have been exhausted, or the request would cause
* the data segment to overlap another segment.
*
* @since Always.
*/
void* sbrk(ptrdiff_t) /* TODO implement sbrk */
__GCC_ONLY(__attribute__((__warn_unused_result__)));
/* TODO implement exit-functions */
__noreturn void _exit(int);
/* TODO implement I/O */
int isatty(int);
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execl(const char*, ... /*, NULL */)
__GCC_ONLY(__attribute__((__sentinel__(0), __nonnull__(1))));
/**
* Replace the current process image with a new process image.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execlp(const char*, ... /*, NULL */)
__GCC_ONLY(__attribute__((__sentinel__(0), __nonnull__(1))));
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execle(const char*, ... /*, NULL, char* const[] */)
__GCC_ONLY(__attribute__((__sentinel__(1), __nonnull__(1))));
#if defined(__SLIBC_SOURCE)
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension, added for completeness.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execlpe(const char*, ... /*, NULL, char* const[] */)
__GCC_ONLY(__attribute__((__sentinel__(1), __nonnull__(1))));
#endif
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execv(const char*, char* const[])
__GCC_ONLY(__attribute__((__nonnull__(1))));
/**
* Replace the current process image with a new process image.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execvp(const char*, char* const[])
__GCC_ONLY(__attribute__((__nonnull__(1))));
/**
* Replace the current process image with a new process image.
*
* @param path The pathname of the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execve(const char*, char* const[], char* const[])
__GCC_ONLY(__attribute__((__nonnull__(1))));
#if defined(__GNU_SOURCE) || defined(__SLIBC_SOURCE)
/**
* Replace the current process image with a new process image.
*
* This is a GNU-compliant slibc extension.
*
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int execvpe(const char*, char* const[], char* const[])
__GCC_ONLY(__attribute__((__nonnull__(1))));
#endif
#if defined(__SLIBC_SOURCE)
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param path The pathname of the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `path` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `path` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execlat(int, const char*, ... /*, NULL, int */)
__GCC_ONLY(__attribute__((__sentinel__(1), __nonnull__(2))));
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `file` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `file` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execlpat(int, const char*, ... /*, NULL, int */)
__GCC_ONLY(__attribute__((__sentinel__(1), __nonnull__(2))));
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param path The pathname of the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `path` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `path` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execleat(int, const char*, ... /*, NULL, char* const[], int */)
__GCC_ONLY(__attribute__((__sentinel__(2), __nonnull__(2))));
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `file` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `file` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execlpeat(int, const char*, ... /*, NULL, char* const[], int */)
__GCC_ONLY(__attribute__((__sentinel__(2), __nonnull__(2))));
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param path The pathname of the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `path` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `path` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execvat(int, const char*, char* const[], int)
__GCC_ONLY(__attribute__((__nonnull__(2))));
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `file` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `file` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execvpat(int, const char*, char* const[], int)
__GCC_ONLY(__attribute__((__nonnull__(2))));
#endif
/**
* Replace the current process image with a new process image.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param path The pathname of the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `path` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `path` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execveat(int, const char*, char* const[], char* const[], int)
__GCC_ONLY(__attribute__((__nonnull__(2))));
#if defined(__SLIBC_SOURCE)
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param dirfd File descriptor for a directory (opened with
* with the open(2) `O_PATH` flag,) that will
* act as the current working directory.
* If `AT_FDCWD`, the current working directory
* will be used.
* @param file The pathname of the file to execute,
* or the filename of a file in $PATH,
* to execute. If $PATH is not set, the current
* working directory (yes, you read that right,)
* and a default value for $PATH will be used.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @param flags Bit mask that can include zero or more of the
* following flags:
* AT_EMPTY_PATH:
* If `file` is an empty string, operate on the
* file (not directory) referred to by `dirfd`.
* AT_SYMLINK_NOFOLLOW:
* If `file` is relative is a symbolic link,
* fail with `errno` set to `ELOOP`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execveat(2).
*
* @since Always.
*/
int execvpeat(int, const char*, char* const[], char* const[], int)
__GCC_ONLY(__attribute__((__nonnull__(2))));
#endif
#if defined(__SLIBC_SOURCE)
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param fd File descriptor for the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int fexecl(int, ... /*, NULL */)
__GCC_ONLY(__attribute__((__sentinel__(0))));
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param fd File descriptor for the file to execute.
* @param ... The arguments with which to execute the file.
* The arguments should have the type `const char*`.
* As a slibc extension, it can be empty.
* This list shall be terminated by a `NULL` sentinel.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int fexecle(int, ... /*, NULL, char* const[] */)
__GCC_ONLY(__attribute__((__sentinel__(1))));
/**
* Replace the current process image with a new process image.
*
* This is a slibc extension.
*
* @param fd File descriptor for the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int fexecv(int, char* const[]);
#endif
/**
* Replace the current process image with a new process image.
*
* @param fd File descriptor for the file to execute.
* @param argv The arguments with which to execute the file.
* This parameter should really have the type
* `const char* const[]`, but that probably not
* so because compiles take issue with casts
* adding const to any pointer in the type
* except the outmost pointer. This list shall
* be `NULL`-terminated. The behaviour is
* system-dependant if this argument is `NULL`.
* @param envp The list of environment variables the new program shall
* have set. Each element shall be formatted $name=$value.
* This list shall be `NULL`-terminated. The behaviour
* is system-dependant if this argument is `NULL`.
* @return This function does not return on success,
* on error, -1 is returned and `errno` is
* set to describe the error.
*
* @throws Any error specified for execve(2).
*
* @since Always.
*/
int fexecve(int, char* const[], char* const[]);
#endif
/*
TODO readn(plan9), writen, preadn, pwriten
readn: read that can only return with a short read on error
writen: write that can only return with a short write on error
preadn: pread that can only return with a short read on error
pwriten: pwrite that can only return with a short write on error
*/
