4.1cBSD/usr/src/ucb/lisp/lisplib/manual/ch5.r
CHAPTER 5
Input/Output
The following functions are used to read and write to and
from external devices and programs (through pipes). All I/O
goes through the lisp data type called the port. A port may
be open for either reading or writing but not both simul-
taneously. There are only a limited number of ports (20)
and they will not be reclaimed unless they are _c_l_o_s_ed. All
ports are reclaimed by a _r_e_s_e_t_i_o call but this drastic step
won't be necessary if the program closes what it uses. If a
port argument is not supplied to a function which requires
one or if a bad port argument (such as nil) is given, then
FRANZ LISP will use the default port according to this
scheme: If input is being done then the default port is the
value of the symbol _p_i_p_o_r_t and if output is being done then
the default port is the value of the symbol _p_o_p_o_r_t. Furth-
ermore if the value of piport or poport is not a valid port
then the standard input or standard output will be used,
respectively. The standard input and standard output are
usually the keyboard and terminal display unless your job is
running in the background and its input or output is con-
nected to a pipe. All output which goes to the standard
output will also go to the port _p_t_p_o_r_t if it is a valid
port. Output destined for the standard output will not
reach the standard output if the symbol ^_w is non nil
(although it will still go to _p_t_p_o_r_t if _p_t_p_o_r_t is a valid
port).
(cfasl 'st_file 'st_entry 'st_funcname ['st_disc
['st_library]])
RETURNS: t
SIDE EFFECT: This is used to load in a foreign function
(see 8.4). The object file st_file is
loaded into the lisp system. St_entry
should be an entry point in the file just
loaded. The function binding of the sym-
bol s_funcname will be set to point to
st_entry, so that when the lisp function
s_funcname is called, st_entry will be
run. st_disc is the discipline to be
given to s_funcname. st_disc defaults to
"subroutine" if it is not given or if it
is given as nil. If st_library is non
nil, then after st_file is loaded, the
libraries given in st_library will be
searched to resolve external references.
Input/Output 5-1
Input/Output 5-2
The form of st_library should be something
like "-lS -lm". The c library (" -lc " )
is always searched so when loading in a C
file you probably won't need to specify a
library. For Fortran files, you should
specify "-lF77" and if you are doing any
I/O that should be "-lF77 -lIf77". For
Pascal files "-lpc" is required.
NOTE: This function may be used to load the output of
the assembler, C compiler, Fortran compiler, and
Pascal compiler but NOT the lisp compiler (use
_f_a_s_l for that). If a file has more than one
entry point, then use _g_e_t_a_d_d_r_e_s_s to locate and
setup other foreign functions.
It is an error to load in a file which has a glo-
bal entry point of the same name as a global
entry point in the running lisp. As soon as you
load in a file with _c_f_a_s_l, its global entry
points become part of the lisp's entry points.
Thus you cannot _c_f_a_s_l in the same file twice
unless you use _r_e_m_o_v_e_a_d_d_r_e_s_s to change certain
global entry points to local entry points.
(close 'p_port)
RETURNS: t
SIDE EFFECT: the specified port is drained and closed,
releasing the port.
NOTE: The standard defaults are not used in this case
since you probably never want to close the stan-
dard output or standard input.
(cprintf 'st_format 'xfst_val ['p_port])
RETURNS: xfst_val
SIDE EFFECT: The UNIX formatted output function printf
is called with arguments st_format and
xfst_val. If xfst_val is a symbol then
its print name is passed to printf. The
format string may contain characters which
are just printed literally and it may con-
tain special formatting commands preceded
by a percent sign. The complete set of
formatting characters is described in the
UNIX manual. Some useful ones are %d for
printing a fixnum in decimal, %f or %e for
printing a flonum, and %s for printing a
character string (or print name of a sym-
bol).
Printed: September 21, 1982
Input/Output 5-3
EXAMPLE: (_c_p_r_i_n_t_f "_P_i _e_q_u_a_l_s %_f" _3._1_4_1_5_9) prints `Pi
equals 3.14159'
(drain ['p_port])
RETURNS: nil
SIDE EFFECT: If this is an output port then the charac-
ters in the output buffer are all sent to
the device. If this is an input port then
all pending characters are flushed. The
default port for this function is the
default output port.
(fasl 'st_name ['st_mapf ['g_warn]])
WHERE: st_mapf and g_warn default to nil.
RETURNS: t if the function succeeded, nil otherwise.
SIDE EFFECT: this function is designed to load in an
object file generated by the lisp compiler
Liszt. File names for object files usu-
ally end in `.o', so _f_a_s_l will append
`.o' to st_name (if it is not already
present). If st_mapf is non nil, then it
is the name of the map file to create.
_F_a_s_l writes in the map file the names and
addresses of the functions it loads and
defines. Normally the map file is created
(i.e. truncated if it exists), but if
(_s_s_t_a_t_u_s _a_p_p_e_n_d_m_a_p _t) is done then the map
file will be appended. If g_warn is non
nil and if a function is loaded from the
file which is already defined, then a
warning message will be printed.
NOTE: _f_a_s_l only looks in the current directory for the
file to load. The function _l_o_a_d looks through a
user supplied search path and will call _f_a_s_l if
it finds a file with the same root name and a
".o" extension. In most cases the user would be
better off using the function _l_o_a_d rather than
calling _f_a_s_l directly.
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9 Printed: September 21, 1982
Input/Output 5-4
(ffasl 'st_file 'st_entry 'st_funcname ['st_discipline
['st_library]])
RETURNS: the binary object created.
SIDE EFFECT: the fortran object file st_file is loaded
into the lisp system. St_entry should be
an entry point in the file just loaded. A
binary object will be created and its
entry field will be set to point to
st_entry. The discipline field of the
binary will be set to st_discipline or
"subroutine" by default. If st_library is
present and non nil, then after st_file is
loaded, the libraries given in st_library
will be searched to resolve external
references. The form of st_library should
be something like "-lS -ltermcap". In any
case, the standard fortran libraries will
be searched also to resolve external
references.
NOTE: in F77 on Unix, the entry point for the fortran
function foo is named `_foo_'.
(filepos 'p_port ['x_pos])
RETURNS: the current position in the file if x_pos is
not given or else x_pos if x_pos is given.
SIDE EFFECT: If x_pos is given, the next byte to be
read or written to the port will be at
position x_pos.
(flatc 'g_form ['x_max])
RETURNS: the number of characters required to print
g_form using _p_a_t_o_m. If x_max is given, and if
_f_l_a_t_c determines that it will return a value
greater than x_max, then it gives up and
returns the current value it has computed.
This is useful if you just want to see if an
expression is larger than a certain size.
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9 Printed: September 21, 1982
Input/Output 5-5
(flatsize 'g_form ['x_max])
RETURNS: the number of characters required to print
g_form using _p_r_i_n_t. The meaning of x_max is
the same as for flatc.
NOTE: Currently this just _e_x_p_l_o_d_e's g_form and checks
its length.
(fileopen 'st_name 'st_mode)
RETURNS: a port for reading or writing (depending on
st_mode) the file st_name.
SIDE EFFECT: the given file is opened (or created if
opened for writing and it doesn't yet
exist).
NOTE: this function call provides a direct interface to
the operating system's fopen function. The mode
may be more than just "r" for read, "w" for write
or "a" for append. The modes "r+", "w+" and "a+"
permit both reading and writing on a port pro-
vided that _f_s_e_e_k is done between changes in
direction. See the UNIX manual description of
fopen for more details. This routine does not
look through a search path for a given file.
(fseek 'p_port 'x_offset 'x_flag)
RETURNS: the position in the file after the function is
performed.
SIDE EFFECT: this function positions the read/write
pointer before a certain byte in the file.
If x_flag is 0 then the pointer is set to
x_offset bytes from the beginning of the
file. If x_flag is 1 then the pointer is
set to x_offset bytes from the current
location in the file. If x_flag is 2 then
the pointer is set to x_offset bytes from
the end of the file (the bytes between the
end of the file and the new position will
be filled with zeroes).
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9 Printed: September 21, 1982
Input/Output 5-6
(infile 's_filename)
RETURNS: a port ready to read s_filename.
SIDE EFFECT: this tries to open s_filename and if it
cannot or if there are no ports available
it gives an error message.
NOTE: to allow your program to continue on a file not
found error you can use something like:
(_c_o_n_d ((_n_u_l_l (_s_e_t_q _m_y_p_o_r_t (_c_a_r (_e_r_r_s_e_t (_i_n_f_i_l_e
_n_a_m_e) _n_i_l))))
(_p_a_t_o_m '"_c_o_u_l_d_n'_t _o_p_e_n _t_h_e _f_i_l_e")))
which will set myport to the port to read from if
the file exists or will print a message if it
couldn't open it and also set myport to nil. To
simply determine if a file exists, there is a
function named _p_r_o_b_e_f.
(load 's_filename ['st_map ['g_warn]])
RETURNS: t
NOTE: The function of _l_o_a_d has changed since previous
releases of FRANZ LISP and the following descrip-
tion should be read carefully.
SIDE EFFECT: _l_o_a_d now serves the function of both _f_a_s_l
and the old _l_o_a_d. _L_o_a_d will search a user
defined search path for a lisp source or
object file with the filename s_filename
(with the extension .l or .o added as
appropriate). The search path which _l_o_a_d
uses is the value of (_s_t_a_t_u_s _l_o_a_d-_s_e_a_r_c_h-
_p_a_t_h). The default is (|.| /usr/lib/lisp)
which means look in the current directory
first and then /usr/lib/lisp. The file
which _l_o_a_d looks for depends on the last
two characters of s_filename. If
s_filename ends with ".l" then _l_o_a_d will
only look for a file name s_filename and
will assume that this is a FRANZ LISP
source file. If s_filename ends with ".o"
then _l_o_a_d will only look for a file named
s_filename and will assume that this is a
FRANZ LISP object file to be _f_a_s_led in.
Otherwise, _l_o_a_d will first look for
s_filename.o, then s_filename.l and
finally s_filename itself. If it finds
s_filename.o it will assume that this is
an object file, otherwise it will assume
that it is a source file. An object file
is loaded using _f_a_s_l and a source file is
Printed: September 21, 1982
Input/Output 5-7
loaded by reading and evaluating each form
in the file. The optional arguments
st_map and g_warn are passed to _f_a_s_l
should _f_a_s_l be called.
NOTE: _l_o_a_d requires a port to open the file s_filename.
It then lambda binds the symbol piport to this
port and reads and evaluates the forms.
(makereadtable ['s_flag])
WHERE: if s_flag is not present it is assumed to be
nil.
RETURNS: a readtable equal to the original readtable if
s_flag is non nil, or else equal to the
current readtable. See chapter 7 for a
description of readtables and their uses.
(nwritn ['p_port])
RETURNS: the number of characters in the buffer of the
given port but not yet written out to the file
or device. The buffer is flushed automati-
cally after the buffer (of 512 characters) is
filled or when _t_e_r_p_r is called.
(outfile 's_filename ['st_type])
RETURNS: a port or nil
SIDE EFFECT: this opens a port to write s_filename. If
st_type is given and if it is a symbol or
string whose name begins with `a', then
the file will be opened in append mode,
that is the current contents will not be
lost and the next data will be written at
the end of the file. Otherwise, the file
opened is truncated by _o_u_t_f_i_l_e if it
existed beforehand. If there are no free
ports, outfile returns nil.
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9 Printed: September 21, 1982
Input/Output 5-8
(patom 'g_exp ['p_port])
RETURNS: g_exp
SIDE EFFECT: g_exp is printed to the given port or the
default port. If g_exp is a symbol then
the print name is printed without any
escape characters around special charac-
ters in the print name. If g_exp is a
list then _p_a_t_o_m has the same effect as
_p_r_i_n_t.
(pntlen 'xfs_arg)
WHERE: xfs_arg is a fixnum, flonum or symbol.
RETURNS: the number of characters needed to print
xfs_arg.
(portp 'g_arg)
RETURNS: t iff g_arg is a port.
(pp [l_option] s_name1 ...)
RETURNS: t
SIDE EFFECT: If s_name_i has a function binding, it is
pretty-printed, otherwise if s_name_i has a
value then that is pretty-printed. Nor-
mally the output of the pretty-printer
goes to the standard output port poport.
The options allow you to redirect it.
____________________________________________________
_P_P _O_p_t_i_o_n _S_u_m_m_a_r_y
(_F _s__f_i_l_e_n_a_m_e) direct future printing to s_filename
(_P _p__p_o_r_t_n_a_m_e) causes output to go to the port p_portname
(port should be opened previously)
(_E _g__e_x_p_r_e_s_s_i_o_n) evaluate g_expression and don't print
____________________________________________________
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9 Printed: September 21, 1982
Input/Output 5-9
(princ 'g_arg ['p_port])
EQUIVALENT TO: patom.
(print 'g_arg ['p_port])
RETURNS: nil
SIDE EFFECT: prints g_arg on the port p_port or the
default port.
(probef 'st_file)
RETURNS: t iff the file st_file exists.
NOTE: Just because it exists doesn't mean you can read
it.
(pp-form 'g_form ['p_port])
RETURNS: t
SIDE EFFECT: g_form is pretty-printed to the port
p_port (or poport if p_port is not given).
This is the function which _p_p uses. _p_p-
_f_o_r_m does not look for function defini-
tions or values of variables, it just
prints out the form it is given.
(ratom ['p_port ['g_eof]])
RETURNS: the next atom read from the given or default
port. On end of file, g_eof (default nil) is
returned.
(read ['p_port ['g_eof]])
RETURNS: the next lisp expression read from the given
or default port. On end of file, g_eof
(default nil) is returned.
NOTE: An error will occur if the reader is given an ill
formed expression. The most common error is too
many right parentheses (note that this is not
considered an error in Maclisp).
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9 Printed: September 21, 1982
Input/Output 5-10
(readc ['p_port ['g_eof]])
RETURNS: the next character read from the given or
default port. On end of file, g_eof (default
nil) is returned.
(readlist 'l_arg)
RETURNS: the lisp expression read from the list of
characters in l_arg.
(removeaddress 's_name1 ['s_name2 ...])
RETURNS: nil
SIDE EFFECT: the entries for the s_name_i in the Lisp
symbol table are removed. This is useful
if you wish to _c_f_a_s_l or _f_f_a_s_l in a file
twice, since it is illegal for a symbol in
the file you are loading to already exist
in the lisp symbol table.
(resetio)
RETURNS: nil
SIDE EFFECT: all ports except the standard input, out-
put and error are closed.
(setsyntax 's_symbol 's_synclass ['ls_func])
RETURNS: t
SIDE EFFECT: this sets the code for s_symbol to sx_code
in the current readtable. If s_synclass
is _m_a_c_r_o or _s_p_l_i_c_i_n_g then ls_func is the
associated function. See Chapter 7 on
the reader for more details.
(tab 'x_col ['p_port])
SIDE EFFECT: enough spaces are printed to put the cur-
sor on column x_col. If the cursor is
beyond x_col to start with, a _t_e_r_p_r is
done first.
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9 Printed: September 21, 1982
Input/Output 5-11
(terpr ['p_port])
RETURNS: nil
SIDE EFFECT: a terminate line character sequence is
sent to the given port or the default
port. This will also flush the buffer.
(terpri ['p_port])
EQUIVALENT TO: terpr.
(tyi ['p_port])
RETURNS: the fixnum representation of the next charac-
ter read. On end of file, -1 is returned.
(tyipeek ['p_port])
RETURNS: the fixnum representation of the next charac-
ter to be read.
NOTE: This does not actually read the character, it
just peeks at it.
(tyo 'x_char ['p_port])
RETURNS: x_char.
SIDE EFFECT: the character whose fixnum representation
is x_code, is printed as a on the given
output port or the default output port.
(untyi 'x_char ['p_port])
SIDE EFFECT: x_char is put back in the input buffer so
a subsequent _t_y_i or _r_e_a_d will read it
first.
NOTE: a maximum of one character may be put back.
(zapline)
RETURNS: nil
SIDE EFFECT: all characters up to and including the
line termination character are read and
discarded from the last port used for
input.
NOTE: this is used as the macro function for the semi-
colon character when it acts as a comment charac-
ter.
Printed: September 21, 1982