INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) NAME NAME NAME NAME intro - introduction to system calls and error numbers SYNOPSIS SYNOPSIS SYNOPSIS SYNOPSIS #include DESCRIPTION DESCRIPTION DESCRIPTION DESCRIPTION This section describes all of the system calls. Most of these calls have one or more error returns. An error condition is indicated by an otherwise impossible returned value. This is almost always -1; the individual descriptions specify the details. An error number is also made available in the external variable errno . Errno is not cleared on successful calls, so it should be tested only after an error has been indicated. All of the possible error numbers are not listed in each system call description because many errors are possible for most of the calls. The following is a complete list of the error numbers and their names as defined in . 1 EPERM Not owner Typically this error indicates an attempt to modify a file in some way forbidden except to its owner or super-user. It is also returned for attempts by ordinary users to do things allowed only to the super- user. 2 ENOENT No such file or directory This error occurs when a file name is specified and the file should exist but doesn't, or when one of the directories in a path name does not exist. 3 ESRCH No such process No process can be found corresponding to that specified by pid in kill or ptrace . 4 EINTR Interrupted system call An asynchronous signal (such as interrupt or quit), which the user has elected to catch, occurred during a system call. If execution is resumed after processing the signal, it will appear as if the interrupted system call returned this error condition. 5 EIO I/O error Some physical I/O error. This error may in some cases occur on a call following the one to which it actually applies. 6 ENXIO No such device or address I/O on a special file refers to a subdevice which does not exist, or beyond the limits of the device. It may Hewlett-Packard - 1 - (printed 12/12/84) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) also occur when, for example, a tape drive is not on- line or no disk pack is loaded on a drive. 7 E2BIG Arg list too long An argument list longer than 5,120 bytes is presented to a member of the exec family. 8 ENOEXEC Exec format error A request is made to execute a file which, although it has the appropriate permissions, does not start with a valid magic number (see a.out (5)). 9 EBADF Bad file number Either a file descriptor refers to no open file, or a read (respectively write) request is made to a file which is open only for writing (respectively reading). 10 ECHILD No child processes A wait , was executed by a process that had no existing or unwaited-for child processes. 11 EAGAIN No more processes A fork , failed because the system's process table is full or the user is not allowed to create any more processes. 12 ENOMEM Not enough space During an exec , brk , or sbrk , a program asks for more space than the system is able to supply. This is not a temporary condition; the maximum space size is a system parameter. The error may also occur if the arrangement of text, data, and stack segments requires too many segmentation registers, or if there is not enough swap space during a fork . 13 EACCES Permission denied An attempt was made to access a file in a way forbidden by the protection system. 14 EFAULT Bad address The system encountered a hardware fault in attempting to use an argument of a system call. 15 ENOTBLK Block device required A non-block file was mentioned where a block device was required, e.g., in mount . 16 EBUSY Mount device busy An attempt to mount a device that was already mounted or an attempt was made to dismount a device on which there is an active file (open file, current directory, mounted-on file, active text segment). It will also Hewlett-Packard - 2 - (printed 12/12/84) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) occur if an attempt is made to enable accounting when it is already enabled. 17 EEXIST File exists An existing file was mentioned in an inappropriate context, e.g., link . 18 EXDEV Cross-device link A link to a file on another device was attempted. 19 ENODEV No such device An attempt was made to apply an inappropriate system call to a device; e.g., read a write-only device. 20 ENOTDIR Not a directory A non-directory was specified where a directory is required, for example in a path prefix or as an argument to chdir (2). 21 EISDIR Is a directory An attempt to write on a directory. 22 EINVAL Invalid argument Some invalid argument (e.g., dismounting a non-mounted device; mentioning an undefined signal in signal , or kill ; reading or writing a file for which lseek has generated a negative pointer). Also set by the math functions described in the (3M) entries of this manual. 23 ENFILE File table overflow The system's table of open files is full, and temporarily no more opens can be accepted. 24 EMFILE Too many open files No process may have more than 20 file descriptors open at a time. 25 ENOTTY Not a typewriter 26 ETXTBSY Text file busy An attempt to execute a pure-procedure program which is currently open for writing (or reading). Also an attempt to open for writing a pure-procedure program that is being executed. 27 EFBIG File too large The size of a file exceeded the maximum file size (1,082,201,088 bytes) or ULIMIT; see ulimit (2). 28 ENOSPC No space left on device During a write to an ordinary file, there is no free space left on the device. Hewlett-Packard - 3 - (printed 12/12/84) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) 29 ESPIPE Illegal seek An lseek was issued to a pipe. 30 EROFS Read-only file system An attempt to modify a file or directory was made on a device mounted read-only. 31 EMLINK Too many links An attempt to make more than the maximum number of links (1000) to a file. 32 EPIPE Broken pipe A write on a pipe for which there is no process to read the data. This condition normally generates a signal; the error is returned if the signal is ignored. 33 EDOM Math argument The argument of a function in the math package (3M) is out of the domain of the function. 34 ERANGE Result too large The value of a function in the math package (3M) is not representable within machine precision. DEFINITIONS DEFINITIONS DEFINITIONS DEFINITIONS Process ID Process ID Process ID Process ID Each active process in the system is uniquely identified by a positive integer called a process ID. The range of this ID is from 0 to 30,000. Parent Process ID Parent Process ID Parent Process ID Parent Process ID A new process is created by a currently active process; see fork (2). The parent process ID of a process is the process ID of its creator. Process Group ID Process Group ID Process Group ID Process Group ID Each active process is a member of a process group that is identified by a positive integer called the process group ID. This ID is the process ID of the group leader. This grouping permits the signaling of related processes; see kill (2). Tty Group ID Tty Group ID Tty Group ID Tty Group ID Each active process can be a member of a terminal group that is identified by a positive integer called the tty group ID. This grouping is used to terminate a group of related process upon termination of one of the processes in the group; see exit (2) and signal (2). Real User ID and Real Group ID Real User ID and Real Group ID Real User ID and Real Group ID Real User ID and Real Group ID Each user allowed on the system is identified by a positive integer called a real user ID. Hewlett-Packard - 4 - (printed 12/12/84) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) Each user is also a member of a group. The group is identified by a positive integer called the real group ID. An active process has a real user ID and real group ID that are set to the real user ID and real group ID, respectively, of the user responsible for the creation of the process. Effective User ID and Effective Group ID Effective User ID and Effective Group ID Effective User ID and Effective Group ID Effective User ID and Effective Group ID An active process has an effective user ID and an effective group ID that are used to determine file access permissions (see below). The effective user ID and effective group ID are equal to the process's real user ID and real group ID respectively, unless the process or one of its ancestors evolved from a file that had the set-user-ID bit or set- group ID bit set; see exec (2). Super-user Super-user Super-user Super-user A process is recognized as a super-user process and is granted special privileges if its effective user ID is 0. Special Processes Special Processes Special Processes Special Processes The processes with a process ID of 0 and a process ID of 1 are special processes and are referred to as proc0 " and " proc1. Proc0 is the scheduler. Proc1 is the initialization process ( init ). Proc1 is the ancestor of every other process in the system and is used to control the process structure. File Name. File Name. File Name. File Name. Names consisting of up to 14 characters may be used to name an ordinary file, special file or directory. These characters may be selected from the set of all character values excluding 0 (null) and the ASCII code for / (slash). Note that it is generally unwise to use "*" , "?" , "[" , or "]" as part of file names because of the special meaning attached to these characters by the shell. See sh (1). Path Name and Path Prefix Path Name and Path Prefix Path Name and Path Prefix Path Name and Path Prefix A path name is a null-terminated character string starting with an optional slash ( / ), followed by zero or more directory names separated by slashes, optionally followed by a file name. More precisely, a path name is a null-terminated character string constructed as follows: ::=||/ ::=|/ ::=/|/ Hewlett-Packard - 5 - (printed 12/12/84) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) where is a string of 1 to 14 characters other than the ASCII slash and null, and is a string of 1 to 14 characters (other than the ASCII slash and null) that names a directory. If a path name begins with a slash, the path search begins at the root directory. Otherwise, the search begins from the current working directory. A slash by itself names the root directory. Unless specifically stated otherwise, the null path name is treated as if it named a non-existent file. Directory. Directory. Directory. Directory. Directory entries are called links. By convention, a directory contains at least two links, and referred to as dot and dot-dot respectively. Dot refers to the directory itself and dot-dot refers to its parent directory. Root Directory and Current Working Directory. Root Directory and Current Working Directory. Root Directory and Current Working Directory. Root Directory and Current Working Directory. Each process has associated with it a concept of a root directory and a current working directory for the purpose of resolving path name searches. A process's root directory need not be the root directory of the root file system. File Access Permissions. File Access Permissions. File Access Permissions. File Access Permissions. Read, write, and execute/search permissions on a file are granted to a process if one or more of the following are true: The process's effective user ID is super-user. The process's effective user ID matches the user ID of the owner of the file and the appropriate access bit of the ``owner'' portion (0700) of the file mode is set. The process's effective user ID does not match the user ID of the owner of the file, and the process's group ID matches the group of the file and the appropriate access bit of the ``group'' portion (070) of the file mode is set. The process's effective user ID does not match the user ID of the owner of the file, and the process's effective group ID does not match the group ID of the file, and the appropriate access bit of the ``other'' portion (07) of the file mode is set. Otherwise, the corresponding permissions are denied. SEE ALSO SEE ALSO SEE ALSO SEE ALSO Hewlett-Packard - 6 - (printed 12/12/84) Hewlett-Packard - 6 - (printed 12/12/84) Hewlett-Packard - 6 - (printed 12/12/84) Hewlett-Packard - 6 - (printed 12/12/84) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) INTRO(2) HP Integral PC INTRO(2) intro(3). Hewlett-Packard - 7 - (printed 12/12/84)