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.TH COSHELL 3

.SH NAME \" @(#)coshell.3 (gsf@research.att.com) 10/11/90

coshell \- shell coprocess support

.SH SYNOPSIS

.L "#include <coshell.h>"

.br

.L "\-lcoshell \-last"

.SH DESCRIPTION

The

.I coshell

routines support the shell as a coprocess.

This coprocess may be either

.IR ksh (1)

or

.IR sh (1)

executing on the local host, or it may be

.IR coshell (1)

with access to shells on hosts throughout the local network.

.PP

The coshell inherits the environment of the calling process.

Signals sent to the calling process are passed to the coshell.

.PP

More than one coshell may be open in the current process.

If the

.L Coshell_t*

argument to the

.LR cowait() ,

.LR cokill() ,

.LR copending() ,

.LR cozombie() ,

or

.L coclose()

calls below is

.L 0

then the call is applied to all open coshell.

.PP

.L "Coshell_t* coopen(const char* shell, int flags, const char* attributes)"

.PP

Returns a pointer to a new coshell.

.L NULL

is returned on error.

If

.L shell

is

.L NULL

then the coshell executable is determined by doing the usual path search,

in order, on the value of the environment variable

.B COSHELL

and the commands

.BR ksh

and

.BR sh .

.L flags

is the inclusive-or of the following:

.TP

.L CO_ANY

Return a pointer to a previously opened coshell if possible, otherwise

open a new coshell.

.TP

.L CO_DEBUG

Enable library debug tracing.

.TP

.L CO_IGNORE

Ignore any command errors.

By default any command error that is not tested by a condtional causes

the job to terminate.

.TP

.L CO_LOCAL

Commands are to be executed on the local host only.

.TP

.L CO_SHELL

The caller is

.BR sh (1):

internal file descriptors are moved to 10 or above;

SIGSTOP and SIGCONT handlers are not installed.

.TP

.L CO_SILENT

Don't trace commands.

By default commands are traced using the shell

.B \-x

option.

.TP

.L CO_NONBLOCK

Normally

.L coexec()

blocks when the job queue is full and waits until a job completes.

.L CO_NONBLOCK

causes

.L coexec()

to return

.L NULL

when the job queue is full.

.PP

.L attributes

is a string that is interpreted by the coshell.

If

.L attributes

is

.L NULL

then the value of the environment variable

.B COATTRIBUTES

is used if defined.

.B ksh

and

.B sh

ignore this string.

The return value points to a structure with the following readonly elements:

.TP

.L "int flags"

The default flags.

.TP

.L "int outstanding"

The number of jobs that have not been waited for.

.TP

.L "int running"

The number of jobs still running.

.TP

.L "int total"

The total number of jobs sent to the coshell.

.TP

.L "unsigned long user"

The total user time of all completed jobs in

.L 1/CO_QUANT

second increments.

.TP

.L "unsigned long sys"

The total system time of all completed jobs in

.L 1/CO_QUANT

second increments.

.PP

.L "int coclose(Coshell_t* sh)"

.PP

Close an open coshell pointed to by

.LR sh .

The coshell exit status is returned.

.PP

.L "Cojob_t* coexec(Coshell_t* sh, const char* cmd, int flags, const char* out, const char* err, const char* att)"

.PP

Sends the shell command line

.L cmd

to the open coshell pointed to by

.L sh

for execution.

.L flags

are the same as in the

.L coopen()

call, and are used to augment the default settings from

.LR coopen() .

.L out

is the standard output file name and defaults to

.B stdout

if

.LR NULL .

.L err

is the standard error file name and defaults to

.B stderr

if

.LR NULL .

.LR att ,

if

.RL non- NULL ,

contains job attributes that are appended to the attributes from

.L coopen()

before being sent to the coshell.

The return value points to a structure with the following elements:

.TP

.L "int id"

A number that uniquely identifies the job within the coshell.

.TP

.L "int status"

The job exit status, valid only for job pointers returned by

.LR cowait() .

.TP

.L "int flags"

The flags enabled for this job.

.TP

.L "void* local"

A user reserved pointer, initially set to

.L NULL

on return from

.LR coexec() .

This is the only job field that may be modified by the user.

The user defined value is preserved until after the

.L cowait()

call that returns the job pointer.

.TP

.L "unsigned long user"

The user time of this job in

.L 1/CO_QUANT

second increments, valid only for job pointers returned by

.LR cowait() .

.TP

.L "unsigned long sys"

The system time of this job in

.L 1/CO_QUANT

second increments, valid only for job pointers returned by

.LR cowait() .

.PP

.L "Cojob_t* cowait(Coshell_t* sh, Cojob_t* job, int timeout)"

.PP

Returns the job pointer in the coshell pointed to by

.L sh

for the job pointed to by

.LR job .

If

.L job

is

.L NULL

then a pointer to any completed job is returned.

.L cowait()

blocks until the specified job(s) complete.

.L NULL

is returned on error or if all jobs have completed and

.L errno

is set to EINVAL for coshell communication errors,

ECHILD if

.L job

is

.L NULL

and there are no children, and ESRCH if

.L job

is not

.L NULL

and not an active job.

.L "cozombie(sh)"

is the number of jobs that may be waited for without blocking.

The return value

.LR status ,

.L user

and

.L sys

job fields are set to their final values.

The return value is valid until the next

.LR coexec() ,

.L cowait()

or

.L coclose()

call.

.L timeout

is the maximum time in milliseconds that wait will block.

If the wait times out then 0 is returned.

A negative

.L timeout

waits until a job completes or a signal is received.

.TP

.L "int cojobs(Coshell_t* sh)"

Returns the number of outstanding jobs that are children of the caller.

(Remote jobs or jobs executed by a separate daemon are not counted here.)

.TP

.L "int copending(Coshell_t* sh)"

Returns the number of pending jobs; this is the number of

.L cowait()

calls required to reap all running jobs.

.TP

.L "int cozombie(Coshell_t* sh)"

Returns the number of jobs that have completed but have not been

.L cowait()'d

for.

.TP

.L "int cokill(Coshell_t* sh, Cojob_t* job, int sig)"

The signal

.L sig

is sent to the job pointed to by

.L job

running in the coshell pointed to by

.LR sh .

If

.L job

is

.L NULL

then the signal is sent to all jobs in the coshell.

If both

.L sh

and

.L job

are

.L NULL

then the signal is sent to all jobs in all coshells.

.L \-1

is returned on error,

.L 0

otherwise.

.TP

.L "int cosync(Coshell_t* sh, const char* path, int fd, int mode)"

Sync all outstanding file operations for either the file

.L path

or the file descriptor

.L fd

after its shell action has completed in

.LR sh .

If

.L path

is

.L NULL

then

.L fd

is used.

If

.L fd<0

and

.L mode>=0

then

.L path

is opened using

.L mode.

This is an unfortunate workaround for NFS and remote coshells, and is a

no-op for all real file systems.

It should be called after

.L cowait()

to ensure that all file system cache info has been flushed.

.IR sync (2)

or

.IR fsync (2)

must still be called to schedule file data to be written to disk.

.TP

.L "char* coinit(Coshell_t* sh)"

Returns the shell initialization commands for the next job.

These commands represent process state changes that may have occurred

since the last call to

.L coinit(),

e.g., current working directory or umask.

If

.L sh

is local (a child of the calling process)

.L coinit()

may return the empty string;

if

.L sh

is remote then considerably more information may be returned.

This routine is used by remote coshell implementations and is

not normally called from user code.

.TP

.L "void coquote(Sfio_T* sp, const char* string, int type)"

Applies shell single quoting to

.L string

and copies the result into the sfio stream

.L sp.

If

.L type!=0

then any occurence of \f5/\fP\fIhosttype\fP\f5/\fP is translated to

\f5/$HOSTTYPE/\fP, where

.I hosttype

is the current value of the

.L HOSTTYPE

environment variable.

This routine is used by remote coshell implementations and is

not normally called from user code.

.SH CAVEATS

.L cosync()

is a hack workaround, but we do have to work in the real world.

.PP

A bug in

.IR bsh (1)

and

.IR ksh (1)

implementations up to and including ksh88e causes some interrupted

jobs to return 0 exit status.

This should be fixed in later shell releases.

.PP

.L "trap 0"

is reserved by

.L coexec()

at the outermost scope.

To use

.L "trap 0"

use

.L "(...)"

to force a subshell.

.SH "SEE ALSO"

coshell(1), ksh(1), nmake(1), sh(1), cs(3), libast(3)