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From: im4u!caip!hplabs!hpda!hpisoa1!davel@sally.utexas.edu (Dave Lennert) Date: Thu, 9 Oct 86 14:06:30 pdt Attached is the P1003 job control proposal. The first file contains the text as accepted at the September P1003 meeting in Palo Alto. Note that this text sometimes replaces, and sometimes augments, existing POSIX text. The second file contains the problems noticed since then and the proposed resolutions. Dave Lennert ucbvax!hpda!davel [UUCP] Hewlett-Packard - 47UX ihnp4!hplabs!hpda!davel [UUCP] 19447 Pruneridge Ave. hpda!davel@ucb-vax.ARPA [ARPA] Cupertino, CA 95014 (408) 447-6325 [AT&T] # This is a shell archive. Remove anything before this line, # then unpack it by saving it in a file and typing "sh file". # # Wrapped by davel at hpisoa1 on Thu Oct 9 13:23:24 1986 # # This archive contains: # acceptedtext problems # echo x - acceptedtext cat >acceptedtext <<'@EOF' IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 2.3 General Terms Replace or add the following definitions: job control option Job control allows users to selectively stop (suspend) the execution of processes and continue (resume) their execution at a later point. The user typically employs this facility via the interactive interface jointly supplied by the terminal I/O driver and a command interpreter. Conforming implementations may optionally support job control facilities (see Symbolic Constants 2.10). Portions of the standard operating system interface which are required only on implementations which support the job control option are so labelled. process group leader A process group leader is a process whose process ID is the same as its process group ID. Any process that is not a process group leader may detach itself from its process group and becomes the process group leader of a new process group by calling either the setpgrp() or setpgrp2() function, which can cause a process to become either a session process group leader or a job process group leader, respectively. Job process group leaders can exist on implementations which support the job control option. saved process group ID An active process has a saved process group ID that is set to the saved process group ID of the parent process at the time of creation of the process (via the fork() function). It is reset to the process group ID of the process when the process successfully calls one of the exec functions. 2.10 Symbolic Constants Add the following new constant after the IEEE1003 constant defintion: IEEE1003job If this symbol is defined then the implementation supports the job control option. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 3.2.1 Wait for Process Termination Functions: wait(), wait2() 3.2.1.1 Synopsis Add the following at the end of the section: #include <sys/wait.h> int wait2 (stat_loc, options) int *stat_loc; int options; 3.2.1.2 Description Add the following at the end of the section: If the wait2() variant is used, then there are two options available for modifying the behavior of the system call. They may be combined by oring them together. The first is WNOHANG which prevents wait2() from suspending the calling process even if there are children to wait for. In this case, a value of zero is returned indicating there are no children which have stopped or died. If the second option WUNTRACED is set, wait2() will also return information when children of the current process are stopped because they received a SIGTTIN, SIGTTOU, SIGTSTP, or SIGSTOP signal. The wait2() function is provided if the implementation supports the job control option. 3.2.1.3 Returns Add the following at the end of the section: If wait2() is called, the WNOHANG option is used, and there are no stopped or terminated children, then a value of zero is returned. Otherwise, a value of -1 is returned and errno shall be set to indicate the error. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 In section 3.2.2.2 Description of the _exit function replace the paragraph: If the process is a process group leader, the SIGHUP signal may be sent to each process that has a process group ID equal to that of the calling process. with: If the process is a session process group leader, the SIGHUP signal may be sent to each process that has a process group ID equal to that of the calling process; also, all such processes may have their process group ID set to zero. If the implementation supports the job control option and if the calling process has child processes that are stopped, they will be sent SIGHUP and SIGCONT signals. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 3.3.1 Signal Names 3.3.1.2 Description Add the following at the end of the signals list. SIGCLD + child process terminated If the implementation supports the job control option then the following are defined: SIGSTOP # stop (cannot be caught or ignored) SIGTSTP # stop signal generated from keyboard SIGTTIN # background read attempted from control terminal SIGTTOU # background write attempted to control terminal SIGCONT %+ continue after stop + Indicates that the action on SIG_DFL is to ignore the signal, rather than terminate the process. # Indicates that the action on SIG_DFL is to stop rather than terminate the process. % Indicates that the signal will not be held off by a stopped process. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 In section 3.3.2.2 Description of the kill() function, add the following paragraph at the end of the Description section. As a single special case on implementations that support the job control option, the continue signal SIGCONT can be sent to any process that is a descendant of the current process. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 3.3.3 Signal Processing 3.3.3.2 Description Replace the SIG_DFL and SIG_IGN discussions with the following text. (Note that this text needs rewording based on the signal working group decisions from Palo Alto, 9/86. Bob Lenk is planning on merging this text with the proposal he sends you. So you should only have to verify that he has done this.) SIG_DFL - signal specific default action For all signals listed in the table in <signal.h> 3.3.1, unless otherwise indicated the default action is either simple abnormal termination or abnormal termination with actions of the receiving process. The result of abnormal termination with actions is implementation-dependent. Abnormal termination with actions may result in the creation of a file named core in the receiving process's current directory. Such a core file should contain sufficient information to document the state of the process at the time of the signal. For certain indicated signals listed in the table in <signal.h> 3.3.1, the default action is to stop (suspend) the receiving process. While a process is stopped, any additional signals that are sent to the process will be held off until the process is continued. An exception to this is SIGCONT which always causes the receiving process to continue if it is stopped. When a process is continued, pending signals will be processed. For certain indicated signals listed in the table in <signal.h> 3.3.1, the default action is to ignore the signal. Signals not described <signal.h> 3.3.1 may have other default actions. SIG_IGN - ignore signal The signal sig is to be ignored. The signals SIGKILL and SIGSTOP shall not be ignored. Ignoring SIGCLD may cause terminating children to be ignored by the wait functions 3.2.1. At the end of the "function address - catch signal" discussion, replace the statement: The signal SIGKILL cannot be caught. with: The signals SIGKILL and SIGSTOP cannot be caught. 3.3.3.4 Errors Replace: [EINVAL] The value sig is either an illegal signal number or SIGKILL. with: [EINVAL] The value sig is either an illegal signal number, or is equal to SIGKILL or SIGSTOP. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 Replace all of section 4.3.1 with: 4.3.1 Get Process Group ID Functions: getpgrp(), getpgrp2() 4.3.1.1 Synopsis int getpgrp ( ) int getpgrp2 (pid) int pid; 4.3.1.2 Description The getpgrp() function returns the process group ID of the calling process. The getpgrp2() function returns the process group ID of the specified process. If pid is zero, the call applies to the current process. For this to be allowed, the real or effective user ID of the current process must match the real or effective user ID of the referenced process, the effective user ID of the current process must be super-user, or the referenced process must be a descendant of the current process. The saved set-user ID of the referenced process may be checked in place of its effective user ID. The getpgrp2() function is provided if the implementation supports the job control option. 4.3.1.3 Returns The getpgrp() function returns the process group ID of the calling process. Upon successful completion, the getpgrp2() function returns the process group ID of the specified process. Otherwise a value of -1 is returned and errno is set to indicate the error. 4.3.1.4 Errors If the getpgrp2() function returns -1, the value stored in errno may be interpreted as follows: [EPERM] The effective user ID of the current process is not super-user, the real or effective user ID of the current process does not match the real or effective user ID (or saved set-user ID) of the specified process, and the specified process is not a descendant of the current process. [ESRCH] No process can be found corresponding to that specified by pid. 4.3.1.5 References setpgrp() 4.3.2, signal() 3.3.3. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 Replace all of section 4.3.2 with: 4.3.2 Set Process Group Functions: setpgrp(), setpgrp2() 4.3.2.1 Synopsis int setpgrp ( ) int setpgrp2 (pid, pgrp) int pid, pgrp; 4.3.2.2 Description The setpgrp() function sets the process group ID of the calling process to the process ID of the calling process and returns the new process group ID. The calling process becomes a session process group leader. The setpgrp() function relinquishes the process's controlling terminal unless the process is already the process group leader. The setpgrp2() function sets the process group ID of the process specified by pid to be pgrp. If pid is zero, the process group ID of the calling process will be affected. If the affected process's new process group ID is the same as its process ID then the affected process becomes a job control process group leader. The setpgrp2() function does not affect the process's controlling terminal. The setpgrp2() function is provided if the implementation supports the job control option. The following condition must be met for the setpgrp2() function to succeed; otherwise, the error [EINVAL] is returned: The value of pgrp must be in the range of valid process group ID values, or it must be zero ("no process group"). In addition, one or more of the following conditions must be met for the setpgrp2() function to succeed; otherwise, the error [EPERM] is returned: The effective user ID of the calling process is super- user. The affected process is a descendant of the calling process. The real or effective user ID of the calling process matches the real or effective user ID of the affected process. The saved set-user ID of the affected process may be checked in place of its effective user ID. In addition, one or more of the following conditions must be met for the setpgrp2() function to succeed, otherwise, the error [EPERM] is returned: The effective user ID of the calling process is super- user. The value of pgrp matches the saved process group ID of the calling process. All processes with a process ID or process group ID that is the same as pgrp have the same real or effective user ID as the real or effective user ID of the calling process, or are descendants of the calling process. The saved set-user ID of the related processes may be checked in place of their effective user ID. 4.3.2.3 Returns The setpgrp() function returns the value of the new process group ID. Upon successful completion, the setpgrp2() function returns a value of 0. Otherwise, a value of -1 is returned and errno is set to indicate the error. 4.3.2.4 Errors If the setpgrp2() function returns -1, the value stored in errno may be interpreted as follows: [ESRCH] No process can be found corresponding to that specified by pid. [EPERM] The effective user ID of the calling process is not super-user; and the real or effective user ID of the calling process does not match the real or effective user ID (or saved set-user ID) of the specified process; and the specified processes are not descendants of the calling process. [EPERM] The effective user ID of the calling process is not super-user; and the value pgrp does not match the saved process group ID of calling process; and a process exists that is not a descendant of the calling process and whose process ID or process group ID match pgrp, while neither the real or effective user ID (or saved set-user ID) of this process match either the real or effective user ID of the calling process. [EINVAL] The value for pgrp is outside the range of valid process group ID values and is non-zero. 4.3.2.5 References exec 3.1.2, _exit() 3.2.2, fork() 3.1.1, getpid() 4.1.1, kill() 3.3.2, signal() 3.3.3. ---------------------------------------------------------------------- IEEE SYSTEM FOR COMPUTER ENVIRONMENTS Std 1003.1 Alter the forthcoming reliable signals proposal, the sigvector() description, by adding the following paragraph: The sv_flags field can be used to modify the receipt the specified signal. If sig is SIGCLD and the implementation supports the job control option, the following flag bit can be set in sv_flags: SV_CLDSTOP Also generate SIGCLD when children stop @EOF chmod 664 acceptedtext echo x - problems cat >problems <<'@EOF' There are two omissions in the job control specification that have come to light since it was accepted at the P1003 meeting in Palo Alto. There will be forthcoming proposals to correct these. Omission 1: Bob Lenk noticed that, in adding SIGCLD to the required portion of POSIX, we neglected to deal with the issue of what happens when SIGCLD is set to SIG_IGN. Specifically, on ATT this causes terminated children to be invisible to wait*() while on BSD there is no such side effect. Bob Lenk feels the best way to handle this is to disallow conforming applications from setting SIGCLD to SIG_IGN. (There is no advantage to using SIG_IGN over SIG_DFL in the case of SIGCLD anyway.) Bob is planning on submitting a cleanup proposal proposing this. Omission 2: Doug Gwyn pointed out the following omission: The changes to section 3.2.1.2 for wait2() did not contain a description of the returned status information in the case of stopped children. I've submitted a proposal to add the following additional text: [OLD TEXT FOR CONTEXT:] wait2() will also return information when children of the current process are stopped because they received a SIGTTIN, SIGTTOU, SIGTSTP, or SIGSTOP signal. [NEW TEXT:] In this case, the status information can also be interpreted in the following way: If the child process stopped, the 8 bits of status (corresponding to the octal value 0177400) will contain the number of the signal that caused the process to stop and the low order 8 bits corresponding to the octal value 0377 will be set equal to the octal value 0177. @EOF chmod 664 problems exit 0 Volume-Number: Volume 7, Number 53