vlibc/include/unistd.h

#ifndef VLIBC_UNISTD_H
#define VLIBC_UNISTD_H

/*
 * vlibc — <unistd.h>.
 *
 * File descriptors, file I/O, and the access/whence symbolic constants
 * (POSIX.1-2008). Every function here is an unbuffered pass-through to the
 * kernel: failures are reported as -1 (or the fd/offset on success) with
 * errno set by the syscall layer.
 *
 *   Level 1 (onlyposix): read, write, pread, pwrite, open, openat, close,
 *                        lseek, dup, dup2, pipe, fsync, fdatasync, ftruncate,
 *                        sync, access, faccessat.
 *   Level 2 (muslmimic): dup3, pipe2 (Linux extensions), truncate (XSI),
 *                        lseek64 (glibc LFS alias of lseek on x86_64).
 *
 * Process control (todo 20) is declared further down:
 *
 *   Level 1 (onlyposix): fork, exec family (execl/execlp/execle/execv/
 *                        execvp/execve/fexecve), getpid, getppid, getuid,
 *                        geteuid, getgid, getegid, setuid, seteuid, setgid,
 *                        setegid, getgroups, setpgid, getpgrp, setsid.
 *   Level 2 (muslmimic): vfork, setpgrp (obsolescent), setgroups, getpgid,
 *                        getsid, tcgetpgrp, tcsetpgrp (XSI).
 *
 * System limits and options (todo 32) are declared after the process
 * block:
 *
 *   Level 1 (onlyposix): sysconf, pathconf, fpathconf, the _SC_* and _PC_*
 *                        configuration keys.
 *   Level 2 (muslmimic): gethostname, sethostname, gethostid (XSI/BSD
 *                        system identification — NOT POSIX.1-2008 base),
 *                        and the _CS_* keys for confstr().
 *
 * The current-working-directory, link/symlink/readlink, path-removal and
 * *at operations, the terminal-identity and login functions, getopt and
 * confstr (todo 38) come after the system-limits block:
 *
 *   Level 1 (onlyposix): getcwd, chdir, fchdir, readlink, symlink, link,
 *                        unlink, rmdir, linkat, readlinkat, renameat,
 *                        symlinkat, unlinkat, isatty, ttyname, ttyname_r,
 *                        getlogin, getlogin_r, getopt plus the optarg/
 *                        optind/opterr/optopt globals, and confstr (its
 *                        _CS_* key constants are level 2, above).
 *   Level 2 (muslmimic): getwd (obsolescent), chroot, swab (XSI).
 *                        basename/dirname live in <libgen.h> and realpath
 *                        in <stdlib.h> (their POSIX homes), also XSI.
 *
 * uname() and struct utsname live in <sys/utsname.h> (todo 32).
 *
 * The open-flag constants (O_RDONLY, O_CREAT, O_CLOEXEC, ...) belong to
 * <fcntl.h> and are deliberately not defined here; the oflag arguments below
 * are plain int and take their values from that header. The optional mode
 * argument of open/openat is a mode_t supplied only when oflag contains
 * O_CREAT or O_TMPFILE.
 *
 * None of these declarations carry an intent attribute: every function
 * performs I/O with side effects and reports failures through errno, so
 * const/pure would be unsound. The process functions additionally must not
 * be const/pure because their results are process state — marking getpid
 * const, for example, would let the compiler hoist it across fork() and
 * observe the parent's pid inside the child.
 */

#include <vlibc/features.h>

#include <stddef.h>

#include <sys/types.h>

#ifdef __cplusplus
extern "C" {
#endif

/* Level 1 (POSIX base). */

/* Access-check modes for access() and faccessat(). */
#define F_OK 0 /* existence only */
#define X_OK 1 /* execute (search for a directory) */
#define W_OK 2 /* write */
#define R_OK 4 /* read */

/* whence values for lseek() and lseek64() (also defined by <stdio.h>). */
#define SEEK_SET 0 /* from the beginning of the file */
#define SEEK_CUR 1 /* from the current position */
#define SEEK_END 2 /* from the end of the file */

/*
 * Read up to nbyte bytes from fildes into buf and return the number of
 * bytes read, 0 at end of file, or -1 with errno set on error. Unbuffered.
 */
ssize_t
read(int fildes, void *buf, size_t nbyte);

/*
 * Write up to nbyte bytes from buf to fildes and return the number of
 * bytes written, or -1 with errno set on error. Unbuffered.
 */
ssize_t
write(int fildes, const void *buf, size_t nbyte);

/*
 * Read nbyte bytes from fildes starting at offset, without changing the
 * file position; return the number of bytes read, or -1 with errno set.
 */
ssize_t
pread(int fildes, void *buf, size_t nbyte, off_t offset);

/*
 * Write nbyte bytes from buf to fildes starting at offset, without
 * changing the file position; return the number of bytes written, or -1
 * with errno set.
 */
ssize_t
pwrite(int fildes, const void *buf, size_t nbyte, off_t offset);

/*
 * Open path with the oflag access mode (from <fcntl.h>) and return a file
 * descriptor, or -1 with errno set. A mode argument is required — and read
 * from the varargs — only when oflag contains O_CREAT or O_TMPFILE.
 */
int
open(const char *path, int oflag, ...);

/*
 * Like open(), but path is relative to the directory named by fd (use
 * AT_FDCWD from <fcntl.h> for the current working directory). The mode
 * varargs rule is the same as open().
 */
int
openat(int fd, const char *path, int oflag, ...);

/*
 * Close the file descriptor fildes; return 0, or -1 with errno set.
 */
int
close(int fildes);

/*
 * Reposition the file offset of fildes to offset per whence (SEEK_SET,
 * SEEK_CUR, SEEK_END) and return the resulting offset, or (off_t)-1 with
 * errno set. The full 64-bit offset is returned; errno is untouched on
 * success.
 */
off_t
lseek(int fildes, off_t offset, int whence);

/*
 * Duplicate fildes to the lowest-numbered free descriptor; return it, or
 * -1 with errno set. The copy shares the file description (position,
 * flags, locks) with the original.
 */
int
dup(int fildes);

/*
 * Duplicate fildes onto fildes2, closing fildes2 first if it was open;
 * return fildes2, or -1 with errno set. dup2(f, f) returns f without
 * doing anything (POSIX).
 */
int
dup2(int fildes, int fildes2);

/*
 * Create a pipe: fildes[0] becomes the read end, fildes[1] the write end.
 * Return 0, or -1 with errno set. No descriptor flags are set (unlike
 * pipe2, this is plain POSIX).
 */
int
pipe(int fildes[2]);

/*
 * Flush all buffered modifications of fildes and its metadata to stable
 * storage; return 0, or -1 with errno set.
 */
int
fsync(int fildes);

/*
 * Like fsync(), but may skip the metadata work needed only to preserve
 * file contents; return 0, or -1 with errno set.
 */
int
fdatasync(int fildes);

/*
 * Truncate fildes to length bytes; return 0, or -1 with errno set.
 */
int
ftruncate(int fildes, off_t length);

/*
 * Flush all filesystem caches to stable storage. Returns nothing.
 */
void
sync(void);

/*
 * Check accessibility of path under amode (R_OK, W_OK, X_OK, F_OK); return
 * 0, or -1 with errno set. Uses the real IDs of the calling process.
 */
int
access(const char *path, int amode);

/*
 * Like access(), but path is relative to the directory named by fd (use
 * AT_FDCWD for the current working directory) and flag may hold
 * AT_EACCESS; return 0, or -1 with errno set.
 */
int
faccessat(int fd, const char *path, int amode, int flag);

/* Level 1 (POSIX base): process control. */

/*
 * Create a child process that is a copy of the caller: fork() returns 0
 * in the child, the child's pid in the parent, and -1 with errno set on
 * failure.
 *
 * Around the fork, the atfork hook table runs: the prepare handlers in
 * reverse registration order before the fork, then the child handlers in
 * the child and the parent handlers in the parent, both in registration
 * order (POSIX pthread_atfork protocol). The table is registered by
 * pthread_atfork() (todo 45) and is empty — a no-op — in a process
 * without threads.
 */
pid_t
fork(void);

/*
 * Replace the calling process image. Success never returns; -1 with
 * errno set otherwise. execl/execle/execlp take the arguments as a
 * varargs list terminated by (char *)NULL (execle is followed by one
 * final char *const envp[] argument); execv/execvp take an argv array.
 * execvp and execlp search the PATH environment variable (default
 * "/bin:/usr/bin") when file contains no '/'. execv/execvp/execl/execlp
 * use the caller's environment; execve/execle/fexecve take envp.
 */
// NOLINTBEGIN(bugprone-easily-swappable-parameters)
int
execl(const char *path, const char *arg0, ...);

int
execle(const char *path, const char *arg0, ...);

int
execlp(const char *file, const char *arg0, ...);
// NOLINTEND(bugprone-easily-swappable-parameters)

int
execv(const char *path, char *const argv[]);

int
execvp(const char *file, char *const argv[]);

int
execve(const char *path, char *const argv[], char *const envp[]);

/*
 * Like execve, but the image is the open descriptor fd.
 */
int
fexecve(int fd, char *const argv[], char *const envp[]);

/*
 * Process ids. getpid/getppid/getuid/geteuid/getgid/getegid read the
 * kernel's per-process ids; setuid/seteuid/setgid/setegid change them.
 * seteuid/setegid change only the effective id (setresuid/setresgid
 * underneath: Linux has no seteuid/setegid syscall).
 */
pid_t
getpid(void);

pid_t
getppid(void);

uid_t
getuid(void);

uid_t
geteuid(void);

gid_t
getgid(void);

gid_t
getegid(void);

int
setuid(uid_t uid);

int
seteuid(uid_t euid);

int
setgid(gid_t gid);

int
setegid(gid_t egid);

/*
 * Supplementary groups: getgroups fills grouplist with up to gidsetsize
 * group ids and returns the total count (0 can be passed to count only);
 * setgroups (level 2, XSI) installs the list.
 */
int
getgroups(int gidsetsize, gid_t grouplist[]);

/*
 * Session control: setpgid moves pid into process group pgid (0 means
 * the caller / the caller's pid); getpgrp returns the caller's process
 * group; setsid creates a new session with the caller as leader and
 * returns the new session id.
 */
int
setpgid(pid_t pid, pid_t pgid);

pid_t
getpgrp(void);

pid_t
setsid(void);

/* Level 1 (POSIX base): system limits and options. */

/*
 * The configuration keys for sysconf(), pathconf() and fpathconf(), and
 * (level 2) the _CS_* keys for confstr() (todo 38).
 *
 * POSIX defines the _SC_* and _PC_* names and the SEMANTICS of the values
 * the configuration functions return for them, but NOT their numeric
 * values: those are private to each C library (glibc numbers them
 * arbitrarily in <bits/confname.h>, musl in a private table). The values
 * below are vlibc's OWN stable ABI, assigned in declaration order and never
 * reused — program source must pass the symbolic constants, never literal
 * integers. They are deliberately NOT glibc's numbers. Any value outside
 * these enums is unknown to the configuration functions and yields -1
 * without errno (the unsupported-key convention, see below).
 */

/* NOLINTBEGIN(bugprone-reserved-identifier) -- POSIX-mandated _SC_/_PC_ names */
enum
{
    /* Process and file limits (sysconf). */
    _SC_ARG_MAX = 0,      /* max bytes of arguments + environment for exec */
    _SC_CHILD_MAX,        /* max simultaneous processes per real user id */
    _SC_CLK_TCK,          /* clock ticks per second, the times() unit (100) */
    _SC_NGROUPS_MAX,      /* max supplementary group ids */
    _SC_OPEN_MAX,         /* max open file descriptors per process */
    _SC_PAGESIZE,         /* memory page size in bytes (from AT_PAGESZ) */
    _SC_PAGE_SIZE,        /* POSIX synonym of _SC_PAGESIZE */
    _SC_NPROCESSORS_CONF, /* number of processors configured */
    _SC_NPROCESSORS_ONLN, /* number of processors online */
    _SC_PHYS_PAGES,       /* number of physical memory pages */
    _SC_AVPHYS_PAGES,     /* number of currently available memory pages */
    _SC_SYMLOOP_MAX,      /* max symlink traversals while resolving a path */
    _SC_STREAM_MAX,       /* max open standard I/O streams (FOPEN_MAX) */
    _SC_TZNAME_MAX,       /* max bytes in a timezone name */
    _SC_VERSION,          /* POSIX.1 version, 200809L */
    _SC_2_VERSION,        /* POSIX.2 version, 200809L */
    _SC_JOB_CONTROL,      /* 1 if job control is supported */
    _SC_SAVED_IDS,        /* 1 if saved set-user/group-id is supported */
    _SC_HOST_NAME_MAX,    /* max bytes in a host name (excluding NUL) */
    _SC_LOGIN_NAME_MAX,   /* max bytes in a login name */
    _SC_GETPW_R_SIZE_MAX, /* recommended buffer size for getpw*_r */
    _SC_IOV_MAX,          /* max iovec entries in readv/writev */
    _SC_LINE_MAX,         /* max bytes in an input line (POSIX.2) */
    _SC_RE_DUP_MAX,       /* max duplicate regexp interval counts */
    _SC_COLL_WEIGHTS_MAX, /* max weights for collating elements */
    _SC_EXPR_NEST_MAX,    /* max expression nesting in expr(1) */

    /* POSIX option indicators (sysconf). Values follow the _POSIX_*
     * convention: a version value means supported, -1 unsupported. */
    _SC_THREADS,                    /* _POSIX_THREADS */
    _SC_SEMAPHORES,                 /* _POSIX_SEMAPHORES */
    _SC_SHARED_MEMORY_OBJECTS,      /* _POSIX_SHARED_MEMORY_OBJECTS */
    _SC_MESSAGE_PASSING,            /* _POSIX_MESSAGE_PASSING */
    _SC_MONOTONIC_CLOCK,            /* _POSIX_MONOTONIC_CLOCK */
    _SC_TIMERS,                     /* _POSIX_TIMERS */
    _SC_SYNCHRONIZED_IO,            /* _POSIX_SYNCHRONIZED_IO */
    _SC_THREAD_SAFE_FUNCTIONS,      /* _POSIX_THREAD_SAFE_FUNCTIONS */
    _SC_THREAD_ATTR_STACKADDR,      /* _POSIX_THREAD_ATTR_STACKADDR */
    _SC_THREAD_ATTR_STACKSIZE,      /* _POSIX_THREAD_ATTR_STACKSIZE */
    _SC_THREAD_PRIORITY_SCHEDULING, /* _POSIX_THREAD_PRIORITY_SCHEDULING */
    _SC_THREAD_PRIO_INHERIT,        /* _POSIX_THREAD_PRIO_INHERIT */
    _SC_THREAD_PRIO_PROTECT,        /* _POSIX_THREAD_PRIO_PROTECT */
    _SC_THREAD_PROCESS_SHARED,      /* _POSIX_THREAD_PROCESS_SHARED */
    _SC_REALTIME_SIGNALS,           /* _POSIX_REALTIME_SIGNALS */

    /* POSIX.1-2008 option indicators that use plain 1 for supported. */
    _SC_REGEXP,         /* 1 if the RE functions are supported */
    _SC_SHELL,          /* 1 if the shell is supported */
    _SC_XOPEN_VERSION,  /* XSI version, 700 */
    _SC_XOPEN_UNIX,     /* 1 if XSI interfaces are supported */
    _SC_XOPEN_CRYPT,    /* 1 if the crypt function is available */
    _SC_XOPEN_ENH_I18N, /* 1 if enhanced internationalization is present */
    _SC_XOPEN_SHM,      /* 1 if XSI shared memory is present */
    _SC_2_C_BIND,       /* POSIX.2 C-language binding */
    _SC_2_C_DEV,        /* POSIX.2 C-language development utilities */
    _SC_2_FORT_DEV,     /* POSIX.2 FORTRAN development utilities */
    _SC_2_FORT_RUN,     /* POSIX.2 FORTRAN runtime utilities */
    _SC_2_LOCALEDEF,    /* POSIX.2 locale creation utilities */
    _SC_2_SW_DEV,       /* POSIX.2 software development utilities */
    _SC_2_UPE           /* POSIX.2 user-portability utilities */
};

/*
 * The _PC_* keys for pathconf() and fpathconf(). Each names a limit or an
 * option of the FILESYSTEM holding the queried path or descriptor; see the
 * pathconf() documentation below for the supported keys and their values.
 */
enum
{
    _PC_LINK_MAX = 0,       /* max link count of a file */
    _PC_MAX_CANON,          /* max bytes in a terminal canonical input line */
    _PC_MAX_INPUT,          /* max bytes available on a terminal input queue */
    _PC_NAME_MAX,           /* max bytes in a file name (excluding NUL) */
    _PC_PATH_MAX,           /* max bytes in a pathname (excluding NUL) */
    _PC_PIPE_BUF,           /* max bytes atomically writable to a pipe */
    _PC_CHOWN_RESTRICTED,   /* 1 if chown is restricted to the owner */
    _PC_NO_TRUNC,           /* 1 if overlong file names are an error */
    _PC_VDISABLE,           /* the terminal disable character (0 = none) */
    _PC_ASYNC_IO,           /* 200809L if asynchronous I/O is supported */
    _PC_SYNC_IO,            /* 200809L if synchronized I/O is supported */
    _PC_PRIO_IO,            /* 200809L if prioritized I/O is supported */
    _PC_SOCK_MAXBUF,        /* max bytes storable in a socket buffer */
    _PC_FILESIZEBITS,       /* bits in a file size field */
    _PC_REC_INCR_XFER_SIZE, /* recommended increment for transfer sizes */
    _PC_REC_MAX_XFER_SIZE,  /* recommended maximum transfer size */
    _PC_REC_MIN_XFER_SIZE,  /* recommended minimum transfer size */
    _PC_REC_XFER_ALIGN,     /* recommended transfer alignment */
    _PC_ALLOC_SIZE_MIN,     /* minimum bytes of a file allocation */
    _PC_SYMLINK_MAX,        /* max bytes in a symbolic link target */
    _PC_2_SYMLINKS          /* 1 if symlinks support the ".." resolution rule */
};
/* NOLINTEND(bugprone-reserved-identifier) */

/*
 * Query a system configuration value for key name (one of the _SC_* above)
 * and return it as a long. A negative value means the option is not
 * supported or the key is unknown; for unsupported options and for any key
 * outside the _SC_* enum, -1 is returned WITHOUT setting errno (callers
 * must not rely on errno after -1).
 *
 * The supported keys and their vlibc values: _SC_ARG_MAX (2097152),
 * _SC_CHILD_MAX (65535), _SC_CLK_TCK (100, the fixed x86_64 clock-tick
 * rate — see the note in src/misc/sysconf.c, todo 35's times() consumes
 * that same constant), _SC_NGROUPS_MAX (65536), _SC_OPEN_MAX (the current
 * RLIMIT_NOFILE soft limit, 1024 if it cannot be read), _SC_PAGESIZE and
 * _SC_PAGE_SIZE (the memory page size from the AT_PAGESZ auxiliary vector
 * entry, 4096 on x86_64), _SC_NPROCESSORS_CONF and _SC_NPROCESSORS_ONLN
 * (the processor count), _SC_PHYS_PAGES and _SC_AVPHYS_PAGES (physical and
 * available memory page counts), _SC_SYMLOOP_MAX (40), _SC_STREAM_MAX
 * (16), _SC_TZNAME_MAX (6), _SC_VERSION and _SC_2_VERSION (200809L),
 * _SC_JOB_CONTROL, _SC_SAVED_IDS, _SC_REGEXP, _SC_SHELL (1 each),
 * _SC_HOST_NAME_MAX (64), _SC_LOGIN_NAME_MAX (256), _SC_GETPW_R_SIZE_MAX
 * (1024), _SC_IOV_MAX (1024), _SC_LINE_MAX (2048), _SC_RE_DUP_MAX (32767),
 * _SC_COLL_WEIGHTS_MAX (255), _SC_EXPR_NEST_MAX (32), _SC_XOPEN_VERSION
 * (700), _SC_XOPEN_UNIX, _SC_XOPEN_CRYPT, _SC_XOPEN_ENH_I18N, _SC_XOPEN_SHM
 * (1 each), and the thread/option version keys (_SC_THREADS ... _SC_2_UPE,
 * 200809L each).
 */
long
sysconf(int name);

/*
 * Query a configurable limit or option of the filesystem holding path (the
 * _PC_* keys above) and return it as a long; -1 with errno set when path
 * cannot be examined. Fixed values: _PC_LINK_MAX (32000), _PC_MAX_CANON
 * and _PC_MAX_INPUT (255), _PC_PATH_MAX (4096), _PC_PIPE_BUF (4096),
 * _PC_CHOWN_RESTRICTED, _PC_NO_TRUNC and _PC_2_SYMLINKS (1), _PC_VDISABLE
 * (0), _PC_FILESIZEBITS (64), and _PC_REC_MIN_XFER_SIZE,
 * _PC_REC_XFER_ALIGN and _PC_ALLOC_SIZE_MIN (the filesystem block size).
 * _PC_NAME_MAX is the filesystem's f_namelen (255 on ext4/xfs). For keys
 * whose option the filesystem does not provide (_PC_ASYNC_IO, _PC_SYNC_IO,
 * _PC_PRIO_IO, _PC_SOCK_MAXBUF, _PC_REC_INCR_XFER_SIZE,
 * _PC_REC_MAX_XFER_SIZE, _PC_SYMLINK_MAX) and for any key outside the
 * _PC_* enum, -1 is returned WITHOUT setting errno.
 */
long
pathconf(const char *path, int name);

/*
 * Like pathconf(), but the filesystem is the one holding the open
 * descriptor fildes.
 */
long
fpathconf(int fildes, int name);

/* Level 1 (POSIX base): current directory, links, and path operations. */

/*
 * Store the absolute pathname of the current working directory into buf.
 * When buf is NULL, the path is returned in a malloc'd buffer instead
 * (size is then only a hint: 0 grows from a default of 128 bytes, and
 * the buffer is enlarged as the kernel reports ERANGE); the caller must
 * free it. Return buf (or the malloc'd buffer), or NULL with errno set
 * (EINVAL for a non-NULL buf with size 0).
 */
char *
getcwd(char *buf, size_t size);

/*
 * Change the current working directory to path (chdir) or to the
 * directory referred to by the open descriptor fildes (fchdir). Return
 * 0, or -1 with errno set.
 */
int
chdir(const char *path);

int
fchdir(int fildes);

/*
 * Create a symbolic link: path2 is created as a link whose contents are
 * the string path1 (which need not exist). Return 0, or -1 with errno
 * set.
 */
int
symlink(const char *path1, const char *path2);

/*
 * Like symlink(), but the link is created in the directory named by fd
 * when path2 is relative (use AT_FDCWD for the current working
 * directory). Return 0, or -1 with errno set.
 */
int
symlinkat(const char *path1, int fd, const char *path2);

/*
 * Read the contents of the symbolic link path into buf (bufsize bytes,
 * no NUL is appended) and return the number of bytes placed in buf, 0
 * for an empty target, or -1 with errno set. The buffer is not
 * terminated: callers sized for bufsize + 1 append the NUL themselves.
 */
ssize_t
readlink(const char *restrict path, char *restrict buf, size_t bufsize);

/*
 * Like readlink(), but path is resolved in the directory named by fd
 * when relative. Return the number of bytes placed in buf, or -1 with
 * errno set.
 */
ssize_t
readlinkat(int fd, const char *restrict path, char *restrict buf, size_t bufsize);

/*
 * Create a hard link: new is created as a second name for the file old
 * (which must not be a directory and must be on the same filesystem).
 * Return 0, or -1 with errno set.
 */
int
link(const char *old, const char *new);

/*
 * Like link(), but old and new are resolved against the directories
 * named by fd1 and fd2 when relative (AT_FDCWD selects the current
 * working directory) and flag may hold AT_SYMLINK_FOLLOW from <fcntl.h>.
 * Return 0, or -1 with errno set.
 */
int
linkat(int fd1, const char *old, int fd2, const char *new, int flag);

/*
 * Remove the name path (a hard link; symbolic links are removed, not
 * followed). Return 0, or -1 with errno set.
 */
int
unlink(const char *path);

/*
 * Like unlink(), but path is resolved in the directory named by fd when
 * relative and flag may hold AT_REMOVEDIR from <fcntl.h> (making it
 * remove an empty directory instead). Return 0, or -1 with errno set.
 */
int
unlinkat(int fd, const char *path, int flag);

/*
 * Remove the empty directory path. Return 0, or -1 with errno set
 * (ENOTEMPTY/EEXIST when the directory is not empty).
 */
int
rmdir(const char *path);

/*
 * Rename old to new within the filesystem: old is resolved against fd1
 * and new against fd2 (AT_FDCWD for the current working directory). Both
 * names may be directories. Return 0, or -1 with errno set.
 */
int
renameat(int fd1, const char *old, int fd2, const char *new);

/* Level 1 (POSIX base): terminal identity, login name, getopt, confstr. */

/*
 * Test whether fildes refers to a terminal. Return 1 when it does, and
 * 0 otherwise (errno may be set — e.g. EBADF — but the caller must not
 * rely on it after a 0 return).
 */
int
isatty(int fildes);

/*
 * Return the pathname of the terminal open on fildes in a shared static
 * buffer (overwritten by the next call), or NULL with errno set when
 * fildes is not a terminal. ttyname_r stores the path in the caller's
 * name buffer instead and returns 0, or an error NUMBER (ENOTTY when
 * fildes is not a terminal, ERANGE when the name does not fit in
 * namesize).
 */
char *
ttyname(int fildes);

int
ttyname_r(int fildes, char *name, size_t namesize);

/*
 * Return the login name of the user associated with the calling process
 * (the owner of its controlling terminal) in a shared static buffer, or
 * NULL with errno set when the name cannot be determined. getlogin_r
 * stores the name in the caller's buffer and returns 0, or an error
 * number (ERANGE when the name does not fit in namesize).
 */
char *
getlogin(void);

int
getlogin_r(char *name, size_t namesize);

/*
 * Command-line option parsing (POSIX.1-2008). getopt returns the next
 * option character from argv per the option characters in optstring; a
 * character followed by ':' in optstring takes an argument (delivered in
 * optarg). A leading ':' in optstring makes missing-argument errors
 * return ':' silently instead of '?' with a diagnostic to stderr.
 * Return -1 when all options have been consumed: optind then points at
 * the first non-option argument, and "--" terminates the scan.
 */
int
getopt(int argc, char *const argv[], const char *optstring);

/* The getopt option state (POSIX.1-2008 base). */
extern char *optarg; /* the argument of the option just returned */
extern int optind;   /* index of the next argument to scan (init 1) */
extern int opterr;   /* nonzero: write diagnostics to stderr (init 1) */
extern int optopt;   /* the option character that caused an error */

/*
 * Query the implementation-defined string value of configuration name
 * (one of the _CS_* keys above). When buf is not NULL and len is large
 * enough, the value (NUL-terminated) is copied into buf; the return
 * value is the length of the value including the terminating NUL, so a
 * return greater than len means the buffer was too small and nothing was
 * copied. For an unknown name, 0 is returned and errno is set to EINVAL.
 */
size_t
confstr(int name, char *buf, size_t len);

#if VLIBC_LEVEL_GE(2)
/* Level 2 (muslmimic): Linux extensions + XSI + obsolescent. */

/*
 * Store the current working directory into pathname, which must hold at
 * least PATH_MAX bytes. Return pathname, or NULL with errno set.
 * Obsolescent: prefer getcwd().
 */
char *
getwd(char *pathname);

/*
 * Change the process root directory to path (used with chdir by
 * chroot-style confinement). Requires privilege. Return 0, or -1 with
 * errno set. XSI.
 */
int
chroot(const char *path);

/*
 * Copy nbytes bytes from from to to, swapping each adjacent pair of
 * bytes (the odd byte of an odd count is not copied). Used for historic
 * byte-order conversion; returns nothing. XSI.
 */
void
swab(const void *restrict from, void *restrict to, ssize_t nbytes);

/*
 * Like dup2(), but with descriptor flags (O_CLOEXEC from <fcntl.h>) applied
 * atomically; return fildes2, or -1 with errno set. Linux-specific.
 */
int
dup3(int fildes, int fildes2, int flags);

/*
 * Like pipe(), but with descriptor flags (e.g. O_CLOEXEC) applied
 * atomically; return 0, or -1 with errno set. Linux-specific.
 */
int
pipe2(int fildes[2], int flags);

/*
 * Truncate the file named by path to length bytes; return 0, or -1 with
 * errno set. XSI.
 */
int
truncate(const char *path, off_t length);

/*
 * glibc LFS alias of lseek(): on x86_64 the LFS and non-LFS off_t are
 * identical (both 64-bit), so this simply calls lseek(). Provided for
 * source compatibility only.
 */
off_t
lseek64(int fildes, off_t offset, int whence);

/*
 * vfork (obsolescent): like fork(), but the child borrows the parent's
 * address space until it execs or exits.
 */
pid_t
vfork(void);

/*
 * setpgrp (obsolescent): setpgid(0, 0) — the caller becomes the leader
 * of its own process group.
 */
int
setpgrp(void);

/*
 * setgroups (XSI): install the supplementary group list of gidsetsize
 * entries. Requires privilege.
 */
int
setgroups(size_t gidsetsize, const gid_t *grouplist);

/*
 * getpgid/getsid (XSI): the process group / session of pid (0 = the
 * caller).
 */
pid_t
getpgid(pid_t pid);

pid_t
getsid(pid_t pid);

/*
 * Controlling-terminal foreground process group (XSI): tcgetpgrp reads
 * the foreground group of the terminal on fildes; tcsetpgrp makes pgid
 * the foreground group.
 */
pid_t
tcgetpgrp(int fildes);

int
tcsetpgrp(int fildes, pid_t pgid);

/* Level 2 (muslmimic): system identification (XSI / BSD, not POSIX base). */

/*
 * The _CS_* keys for confstr() (todo 38, which owns the function and its
 * string results). Values are vlibc-local ABI like the _SC_ and _PC_ keys
 * above; they are defined here now so todo 38 only implements confstr()
 * itself.
 */
/* NOLINTBEGIN(bugprone-reserved-identifier) -- POSIX-mandated _CS_ names */
enum
{
    _CS_PATH = 0,                       /* value of PATH (always a usable default) */
    _CS_POSIX_V6_WIDTH_RESTRICTED_ENVS, /* 1 if the V6 width-restricted envs exist */
    _CS_POSIX_V7_WIDTH_RESTRICTED_ENVS, /* 1 if the V7 width-restricted envs exist */
    _CS_LFS_CFLAGS,                     /* cpp/cflags for large-file support */
    _CS_LFS_LDFLAGS,                    /* ld flags for large-file support */
    _CS_LFS_LIBS,                       /* libraries for large-file support */
    _CS_LFS_LINTFLAGS,                  /* lint flags for large-file support */
    _CS_LFS64_CFLAGS,                   /* cpp/cflags for large-file64 support */
    _CS_LFS64_LDFLAGS,                  /* ld flags for large-file64 support */
    _CS_LFS64_LIBS,                     /* libraries for large-file64 support */
    _CS_LFS64_LINTFLAGS,                /* lint flags for large-file64 support */
    _CS_GNU_LIBC_VERSION,               /* "glibc X.Y" (vlibc extension) */
    _CS_GNU_LIBPTHREAD_VERSION          /* "NPTL X.Y" (vlibc extension) */
};
/* NOLINTEND(bugprone-reserved-identifier) */

/*
 * Store the NUL-terminated host name of the current machine into name,
 * sized len bytes. Return 0 on success; if the name (including its NUL
 * terminator) does not fit in len bytes, nothing is written beyond the
 * fit and -1 is returned with errno set to ENAMETOOLONG. XSI.
 */
int
gethostname(char *name, size_t len);

/*
 * Set the kernel's host name from name (len bytes, no NUL required).
 * Requires privilege. Return 0, or -1 with errno set. BSD, not POSIX.
 */
int
sethostname(const char *name, size_t len);

/*
 * Return the 32-bit host identifier of the current machine. vlibc returns
 * 0 (musl's behavior): the historic value was derived from the host's
 * primary IP address via gethostbyname, which the modern library does not
 * perform. [OB] — obsolescent in POSIX.
 */
long
gethostid(void);
#endif /* VLIBC_LEVEL_GE(2) */

#ifdef __cplusplus
}
#endif

#endif /* VLIBC_UNISTD_H */