C Library Functions - M_process (3)
NAME
M_process(3fm) - [M_process::INTRO] Fortran Module for calling process-related C functions from Fortran (LICENSE:PD)
CONTENTS
Synopsis
Description
Options
Examples
See Also
Author
License
SYNOPSIS
use M_process, only : process_open_read, process_open_write, process_closeuse M_process, only : process_readline, process_readall, process_writeline
use M_process, only : streampointer, process_debug
DESCRIPTION
Module M_process(3f) lets Fortran code read/write lines from/to processes.These Fortran procedures use the ISO_C_BINDING interface to define Fortran-callable versions of the C procedures popen(3c)/pclose(3c) and fgets(3c)/fputs(3c). A set of record-oriented wrapper routines are then used to create a simple Fortran-callable interface.
A POSIX C interface is generally available but may require using a Linux subwindow or an application such as CygWin on MSWindows platforms.
Basically, you
The procedures defined are:
o Open a process for either reading from or writing to using formatted sequential text records (eg. "lines"); much like with a regular file. o pass a CHARACTER variable to/from the process that represents a record. o Use internal READs and internal WRITEs or parsing routines to create or interpret the lines. o when done close the process much like closing a file.
! open process to read from subroutine process_open_read(cmd,fp,ierr)where the variable types are! open process to write to subroutine process_open_write(cmd,fp,ierr)
! read line from process subroutine process_readline(string,fp,ierr) ! read all of process output into a string string function process_readall(cmd,ierr) result (string)
! write lines to process subroutine process_writeline & & (string|string_array,fp,ierr[,trm=.t.|.f.])
! close process subroutine process_close(fp,ierr)
character(len=*) :: cmd type(streampointer) :: fp character(len=*) :: string integer :: ierr
OPTIONS
maximum character value length is currently 4096
cmd command passed to system to start process fp C file pointer returned by process_open_*() string data line to send or receive from process ierr error flag returned.
o process_writeline(3f) : negative indicates an error o process_readline(3f) : Non-zero indicates an error
EXAMPLES
An example that places all the output of a command into a single string variable (see process_readall(3) for an even simpler way to do this) ...
program read_ex use M_process ,only: process_open_read, process_readline use M_process ,only: streampointer, process_close implicit none ! C file pointer returned by process_open() type(streampointer) :: fp ! check status of calls to process module routines integer :: ierr ! hold results, assuming sufficient memory is available character(len=:),allocatable :: string ! long enough to hold any expected line character(len=4096) :: line string=’’ !###! open process to read from call process_open_read(’ls’,fp,ierr) !###! read output of process till end do call process_readline(line,fp,ierr) if(ierr.ne.0)exit !###! append output lines together string=string//trim(line)//’ ’ write(*,*)’[’//string//’]’ enddo write(*,*)trim(string) !###! Wrap up call process_close(fp,ierr) end program read_exWhen calling a line-mode program from another program the most natural way is to open a process and write to it.
Following is an example program that calls the M_process module to start a plotting program called gnuplot(1) and give it enough commands to generate a plot. It then lets you interactively interact with the gnuplot(1) program or continue on in the program.
program gnuplotExample use M_process ,only: process_open_write, process_writeline use M_process ,only: streampointer, process_close implicit none ! ! Example of Fortran writing GNUPLOT command and data file. ! !*! line of data to write !*! (assumed long enough to hold any command line) character(len=4096) :: line !*! C file pointer returned by process_open() type(streampointer) :: fp !*! check status of calls to process module routines integer :: ierr !*! DO loop counter integer :: i !*! number of points to put into curve to be plotted integer,parameter :: n=50 !*! arrays to fill with curve data to be plotted real :: x(n),y(n) integer :: ios !*! Define sample X,Y array. do i=1,n !*! set X() values as whole numbers 1 to N x(i)=i !*! y(i)=(x(i)+0.5)**2 enddo !*! Write the GnuPlot commands !*! open process to write to (ie. start gnuplot(1) program) call process_open_write(’gnuplot’,fp,ierr) !*! create in-line dataset $SET1 call process_writeline(’$SET1 <<EOD’,fp,ierr) do i=1,n !*! Write the X,Y array as coordinates to be plotted. write(line,’(2(f10.3,1x))’)x(i),y(i) call process_writeline(line,fp,ierr) enddoThis program starts a bash shell that, among other things, calls sqlite3 and gnuplot. In this case the text is fixed to keep the example simple. More typically the text would be conditionally selected or generated by the program.call process_writeline([character(len=128) :: & &’EOD ’, & &’set title " Example of GNUPlot data and command file generation"’, & &’set nokey’ , & &’plot $SET1 with lines’ , & &’’],fp,ierr)
!*! Additional gnuplot commands; in this case interactively entered write(*,’(a)’)’enter gnuplot commands or "." to exit’ do write(*,’(a)’,advance=’no’)’gnu>>’ read(*,’(a)’,iostat=ios)line if(line.eq.’.’)exit call process_writeline(trim(line),fp,ierr) enddo !*! Wrap up call process_close(fp,ierr) write(*,*)’CLOSED THE PROCESS. RETURNING TO PROGRAM’ end program gnuplotExample
program demo_M_process use M_process ,only : process_open_write, process_writeline use M_process ,only : streampointer, process_close implicit none ! C file pointer returned by process_open() type(streampointer) :: fp ! check status of calls to process module routines integer :: ierr character(len=:),allocatable :: text(:)This example shows a routine to read the output of one command and then call another command to write that output to.! open process to write to (ie. start gnuplot(1) program) !!call process_open_write(’cat’,fp,ierr) ! open process to write to (ie. start gnuplot(1) program) call process_open_write(’bash’,fp,ierr)
text=[character(len=128) :: & "rm -f sqlite1.db", & "sqlite3 sqlite1.db <<\EOF", & "-- ***********************************************",& "CREATE TABLE IF NOT EXISTS animals( ",& " name TEXT NOT NULL PRIMARY KEY , ",& " hair INT NOT NULL , ",& " mobility INT NOT NULL , ",& " vision INT NOT NULL ); ",& "-- ***********************************************",& "INSERT INTO animals(& &name,hair,mobility,vision) VALUES(’kittens’,4,5,1);",& "INSERT INTO animals(& &name,hair,mobility,vision) VALUES(’mice’ ,6,7,2);",& "INSERT INTO animals(& &name,hair,mobility,vision) VALUES(’rats’ ,2,3,3);",& "-- ***********************************************",& ".quit", & "EOF", & "##################################################",& "sqlite3 -header -column sqlite1.db ’select * from animals’",& "sqlite3 sqlite1.db & &’select name, hair, mobility, vision from animals’",& "##################################################",& "gnuplot --persist <<\EOF ",& "######################################## ",& "#set terminal gif ",& "#set output ’M_process.3.gif’ ",& "######################################## ",& "#set terminal png ",& "#set output ’bar.png’ ",& "######################################## ",& "#set terminal pdf enhanced ",& "#set output ’bar.pdf’ ",& "######################################## ",& "#set style data lines ",& "######################################## ",& "set datafile separator ""|"" ",& "set style data histogram ",& "set style histogram cluster gap 1 ",& "set style fill solid border rgb ""black"" ",& "set auto x ",& "set yrange [0:*] ",& "plot ""< sqlite3 sqlite1.db & &’select name, hair, mobility, vision from animals’"" \ ", & " using 2:xtic(1) title ""hair"", \ ",& " ’’ using 4:xtic(1) title ""vision"", \ ",& " ’’ using 3:xtic(1) title ""mobility"" ",& "quit ",& "EOF ",& " "]
!!write(*,’(a)’)text call process_writeline(text,fp,ierr) call process_close(fp,ierr) write(*,’(a)’)’CLOSED THE PROCESS. RETURNING TO PROGRAM’
end program demo_M_process
program test implicit none call readit(’ls -l’) call writeit(’cat -n’) containssubroutine readit(cmd) use M_process ,ONLY: process_open_read, process_readline use M_process ,ONLY: streampointer, process_close ! C file pointer returned by process_open() type(streampointer) :: fp ! command line executed to start process character(len=*) :: cmd ! line of data to read (assumed long enough to hold any input line) character(len=4096) :: line integer ierr ! open process to read from call process_open_read(cmd,fp,ierr) write(*,*)’READTEST: process is opened with status ’,ierr ierr=0 do while(ierr .eq. 0) ! read a line from the process call process_readline(line,fp,ierr) if(ierr.ne.0)then write(*,*)’READTEST: ierr is ’,ierr exit endif write(*,*)’READTEST: line:’//trim(line) enddo call process_close(fp,ierr) write(*,*)’READTEST: process closed with status ’,ierr end subroutine readit !--------------------------------------------------------------------- subroutine writeit(cmd) use M_process, only: process_open_write, process_writeline use M_process, only: streampointer, process_close ! C file pointer returned by process_open() type(streampointer) :: fp ! command line executed to start process character(len=*) :: cmd ! line of data to write (assumed long enough to hold any output line) character(len=4096) :: line integer :: ierr integer :: i ! open process to write to call process_open_write(cmd,fp,ierr) write(*,*)’WRITETEST: process is opened’ ierr=0 do i=1,10 write(line,’("WRITETEST: line ",i0)’)i call process_writeline(line,fp,ierr) if(ierr.lt.0)then write(*,*)’WRITETEST: process write error ’,ierr exit endif enddo call process_close(fp,ierr) write(*,*)’WRITETEST: process closed with status ’,ierr end subroutine writeit end program test
SEE ALSO
o PIPES: pipe(3c), popen(3c), pclose(3c), fflush(3c) o NAMED PIPES: mkfifo(3c), mknod(3c) o SUBPROCESSES: fork(3c) o OTHER: fflush(3c)
AUTHOR
John S. Urban
LICENSE
Public Domain
| Nemo Release 3.1 | M_process (3) | February 23, 2025 |
