strchg(1)strchg(1)NAME
strchg, strconf - Alters and queries stream configuration
SYNOPSIS
strchg -h module1 [,module2,... modulen]
strchg -p [-a | -u module]
strchg -f file
strconf [-t | -m module]
The strchg and strconf commands modify and return information about the
configuration of the Stream associated with the user's standard input.
OPTIONS
The strchg command has three formats, which must be specified sepa‐
rately. These formats offer the following options: When used with -p,
removes all of the STREAMS modules above the topmost driver; that is,
the command only affects the uppermost Stream created for a multiplexed
driver, not any of the lower Streams. This option cannot be used with
-u. Specifies a file that contains a list of STREAMS modules to be
pushed on the standard input Stream for a desired configuration. The
names of the modules must occupy separate lines in the file. The strchg
command pushes any module that is desired but is not present on the
Stream, and pops any module that is not desired and is present on the
Stream. Pushes the STREAMS module or modules specified by the module
argument or arguments on the standard input Stream. The command pushes
the STREAMS modules on the Stream in the order that they are specified;
that is, module1 is pushed first, module2 is pushed second, and so
forth. Pops STREAMS modules off the standard input Stream. When the -p
option is specified without any other options, the command removes the
topmost module (the module immediately below the Stream head) from the
Stream. The -a and -u options cannot be used simultaneously with the
-p option. When used with -p, pops all of the modules above the speci‐
fied module off the Stream, leaving that module on it. This option can‐
not be used with -a.
The strconf command options are the following: Prints the name of the
topmost module on the standard input Stream, if this module exists.
Confirms whether or not the specified module module is present on the
Stream.
DESCRIPTION
The strchg command pushes and pops STREAMS modules on and off the
user's standard input Stream to achieve a desired configuration. The
strconf command queries the configuration of the Stream, then prints
the names of the modules and the topmost device driver, or the name of
the topmost module, or the name of a specific module.
When the -f option is used, the strchg command first determines the
current configuration of the standard input Stream, then pushes or pops
the modules named in the file argument to fix it. The module that is
named first is meant to be the one that is located below the Stream
head, while the module named last is meant to be at the bottom of the
Stream, closest to the device driver. This is the opposite of the order
in which the strchg command pushes and pops modules when it is invoked
with the -h option.
To use the strchg command, you must either be the owner of the Stream
or the superuser.
Without options, the strconf command prints the names of all of the
modules, if any, and the name of the topmost driver. Names are printed
one per line, with the driver's name last. When the autopush mechanism
is used in a system, the strconf command returns the names of the mod‐
ules that were automatically pushed on the standard input Stream at the
opening of the associated device. If the Stream configuration has been
changed since the device was opened, the command prints the altered
list of module names.
If the -t option is used, the strconf command prints only the topmost
module's name, if any exists. When the -m option is used, the command
queries the standard input Stream for the module specified in the mod‐
ule argument. If this module is present on the Stream, it prints the
message yes and returns a 0 (zero). If the module is not on the
Stream, strchg prints no and returns a nonzero value. The -t and -m
options cannot be used simultaneously.
To use the strconf command, you must either have read permission or be
the superuser.
For both the strchg and strconf commands, note that if modules are
pushed onto the user's standard input Stream in the wrong order, that
Stream will not function as expected. For example, in the case of ter‐
minal lines (ttys), the line discipline module must be pushed in the
correct place; otherwise, the terminal might not respond correctly to
commands.
EXIT STATUS
The strchg command returns 0 (zero) on success. When the command
encounters an error, it returns a nonzero status and prints an error
message. The command returns errors for such conditions as a usage
error, bad module name, failure of an ioctl system call, and failure to
open the file specified by the -f option.
The strconf command returns 0 (zero) on success and a nonzero status
for errors. It prints an error message for any errors. When the -m and
-t options return successfully, this indicates that the named, or top‐
most, module is present. The error conditions that the command returns
a status for include a usage error and a failure of an ioctl system
call.
EXAMPLES
To print out the names of the modules and driver present on the user's
standard input Stream, enter: strconf To push the fictional line disci‐
pline module linedisp onto the user's standard input Stream, enter:
strchg -h linedisp
The ldterm module is pushed below the Stream head in the user's
standard input Stream. To set up the standard input Stream
(JIS) characters, and to do this using a previously created file
called /$HOME/.mytty.conf that lists the modules, enter: strchg
-f $HOME/.mytty.conf
If the list of modules in the /$HOME/.mytty.conf file is as fol‐
lows, the fictional lpass module will be pushed first, followed
by the fictional linedisp module, followed by the fictional
upass module.
upass linedisp lpass
SEE ALSO
Commands: autopush(8)
Interfaces: streamio(7)strchg(1)
