  
  [1X11 [33X[0;0YProcesses[133X[101X
  
  [33X[0;0Y[5XGAP[105X  can  call other programs, such programs are called [13Xprocesses[113X. There are
  two  kinds of processes: first there are processes that are started, run and
  return  a  result, while [5XGAP[105X is suspended until the process terminates. Then
  there are processes that will run in parallel to [5XGAP[105X as subprocesses and [5XGAP[105X
  can    communicate    and    control    the    processes    using    streams
  (see [2XInputOutputLocalProcess[102X ([14X10.8-2[114X)).[133X
  
  
  [1X11.1 [33X[0;0YProcess and Exec[133X[101X
  
  [1X11.1-1 Process[101X
  
  [29X[2XProcess[102X( [3Xdir[103X, [3Xprg[103X, [3Xstream-in[103X, [3Xstream-out[103X, [3Xoptions[103X ) [32X operation
  
  [33X[0;0Y[2XProcess[102X  runs  a  new  process  and  returns when the process terminates. It
  returns  the  return  value  of the process if the operating system supports
  such a concept.[133X
  
  [33X[0;0YThe  first  argument  [3Xdir[103X  is a directory object (see [14X9.3[114X) which will be the
  current  directory  (in  the  usual UNIX or MSDOS sense) when the program is
  run.  This will only matter if the program accesses files (including running
  other programs) via relative path names. In particular, it has nothing to do
  with finding the binary to run.[133X
  
  [33X[0;0YIn  general  the  directory  will  either be the current directory, which is
  returned  by [2XDirectoryCurrent[102X ([14X9.3-4[114X) –this was the behaviour of [5XGAP[105X 3– or a
  temporary  directory  returned by [2XDirectoryTemporary[102X ([14X9.3-3[114X). If one expects
  that  the  process  creates temporary or log files the latter should be used
  because  [5XGAP[105X  will attempt to remove these directories together with all the
  files in them when quitting.[133X
  
  [33X[0;0YIf  a program of a [5XGAP[105X package which does not only consist of [5XGAP[105X code needs
  to  be  launched in a directory relative to certain data libraries, then the
  first  entry  of  [2XDirectoriesPackageLibrary[102X  ([14X76.3-4[114X)  should  be  used. The
  argument  of  [2XDirectoriesPackageLibrary[102X  ([14X76.3-4[114X)  should be the path to the
  data library relative to the package directory.[133X
  
  [33X[0;0YIf  a  program  calls other programs and needs to be launched in a directory
  containing  the  executables  for such a [5XGAP[105X package then the first entry of
  [2XDirectoriesPackagePrograms[102X ([14X76.3-5[114X) should be used.[133X
  
  [33X[0;0YThe  latter  two  alternatives  should  only be used if absolutely necessary
  because  otherwise  one  risks accumulating log or core files in the package
  directory.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xpath := DirectoriesSystemPrograms();;[127X[104X
    [4X[25Xgap>[125X [27Xls := Filename( path, "ls" );;[127X[104X
    [4X[25Xgap>[125X [27Xstdin := InputTextUser();;[127X[104X
    [4X[25Xgap>[125X [27Xstdout := OutputTextUser();;[127X[104X
    [4X[25Xgap>[125X [27XProcess( path[1], ls, stdin, stdout, ["-c"] );;[127X[104X
    [4X[28Xawk    ls     mkdir[128X[104X
    [4X[25Xgap>[125X [27X# current directory, here the root directory[127X[104X
    [4X[25Xgap>[125X [27XProcess( DirectoryCurrent(), ls, stdin, stdout, ["-c"] );;[127X[104X
    [4X[28Xbin    lib    trans  tst    CVS    grp    prim   thr    two[128X[104X
    [4X[28Xsrc    dev    etc    tbl    doc    pkg    small  tom[128X[104X
    [4X[25Xgap>[125X [27X# create a temporary directory[127X[104X
    [4X[25Xgap>[125X [27Xtmpdir := DirectoryTemporary();;[127X[104X
    [4X[25Xgap>[125X [27XProcess( tmpdir, ls, stdin, stdout, ["-c"] );;[127X[104X
    [4X[25Xgap>[125X [27XPrintTo( Filename( tmpdir, "emil" ) );[127X[104X
    [4X[25Xgap>[125X [27XProcess( tmpdir, ls, stdin, stdout, ["-c"] );;[127X[104X
    [4X[28Xemil[128X[104X
  [4X[32X[104X
  
  [33X[0;0Y[3Xprg[103X  is  the filename of the program to launch, for portability it should be
  the  result  of  [2XFilename[102X  ([14X9.4-1[114X) and should pass [2XIsExecutableFile[102X ([14X9.6-4[114X).
  Note  that  [2XProcess[102X does [13Xno[113X searching through a list of directories, this is
  done by [2XFilename[102X ([14X9.4-1[114X).[133X
  
  [33X[0;0Y[3Xstream-in[103X  is  the input stream that delivers the characters to the process.
  For  portability  it should either be [2XInputTextNone[102X ([14X10.9-1[114X) (if the process
  reads  no  characters),  [2XInputTextUser[102X  ([14X10.6-1[114X),  the  result  of a call to
  [2XInputTextFile[102X  ([14X10.5-1[114X)  from  which  no  characters  have been read, or the
  result of a call to [2XInputTextString[102X ([14X10.7-1[114X).[133X
  
  [33X[0;0Y[2XProcess[102X is free to consume [13Xall[113X the input even if the program itself does not
  require any input at all.[133X
  
  [33X[0;0Y[3Xstream-out[103X  is  the  output  stream  which  receives the characters from the
  process. For portability it should either be [2XOutputTextNone[102X ([14X10.9-2[114X) (if the
  process writes no characters), [2XOutputTextUser[102X ([14X10.6-2[114X), the result of a call
  to  [2XOutputTextFile[102X ([14X10.5-2[114X) to which no characters have been written, or the
  result of a call to [2XOutputTextString[102X ([14X10.7-2[114X).[133X
  
  [33X[0;0Y[3Xoptions[103X is a list of strings which are passed to the process as command line
  argument.  Note  that  no  substitutions are performed on the strings, i.e.,
  they  are  passed  immediately  to  the  process  and are not processed by a
  command  interpreter (shell). Further note that each string is passed as one
  argument,  even  if  it  contains  [13Xspace[113X  characters. Note that input/output
  redirection commands are [13Xnot[113X allowed as [3Xoptions[103X.[133X
  
  [33X[0;0YIn  order  to  find  a  system program use [2XDirectoriesSystemPrograms[102X ([14X9.3-6[114X)
  together with [2XFilename[102X ([14X9.4-1[114X).[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xpath := DirectoriesSystemPrograms();;[127X[104X
    [4X[25Xgap>[125X [27Xdate := Filename( path, "date" );[127X[104X
    [4X[28X"/bin/date"[128X[104X
  [4X[32X[104X
  
  [33X[0;0YThe  next  example  shows how to execute [10Xdate[110X with no argument and no input,
  and collect the output into a string stream.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27Xstr := "";; a := OutputTextString(str,true);;[127X[104X
    [4X[25Xgap>[125X [27XProcess( DirectoryCurrent(), date, InputTextNone(), a, [] );[127X[104X
    [4X[28X0[128X[104X
    [4X[25Xgap>[125X [27XCloseStream(a);[127X[104X
    [4X[25Xgap>[125X [27XPrint(str);[127X[104X
    [4X[28XFri Jul 11 09:04:23 MET DST 1997[128X[104X
  [4X[32X[104X
  
  [1X11.1-2 Exec[101X
  
  [29X[2XExec[102X( [3Xcmd[103X, [3Xoption1[103X, [3X...[103X, [3XoptionN[103X ) [32X function
  
  [33X[0;0Y[2XExec[102X  runs  a shell in the current directory to execute the command given by
  the string [3Xcmd[103X with options [3Xoption1[103X, ..., [3XoptionN[103X.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XExec( "date" );[127X[104X
    [4X[28XThu Jul 24 10:04:13 BST 1997[128X[104X
  [4X[32X[104X
  
  [33X[0;0Y[3Xcmd[103X is interpreted by the shell and therefore we can make use of the various
  features that a shell offers as in following example.[133X
  
  [4X[32X  Example  [32X[104X
    [4X[25Xgap>[125X [27XExec( "echo \"GAP is great!\" > foo" );[127X[104X
    [4X[25Xgap>[125X [27XExec( "cat foo" );[127X[104X
    [4X[28XGAP is great![128X[104X
    [4X[25Xgap>[125X [27XExec( "rm foo" );[127X[104X
  [4X[32X[104X
  
  [33X[0;0Y[2XExec[102X  calls  the  more general operation [2XProcess[102X ([14X11.1-1[114X). The function [2XEdit[102X
  ([14X6.10-1[114X) should be used to call an editor from within [5XGAP[105X.[133X
  
