NSHPOPEN(3)         UNIX Programmer's Manual          NSHPOPEN(3)



NAME
     nshpopen, nshpclose - initiate I/O to/from a process

SYNOPSIS
     #include <stdio.h>

     FILE *nshpopen(command, type)
     char *command, *type;

     nshpclose(stream)
     FILE *stream;

DESCRIPTION
     The arguments to _n_s_h_p_o_p_e_n are pointers to null-terminated
     strings containing respectively a shell command line and an
     I/O mode, either "r" for reading or "w" for writing.  It
     creates a pipe between the calling process and the command
     to be executed.  The value returned is a stream pointer that
     can be used (as appropriate) to write to the standard input
     of the command or read from its standard output.

     A stream opened by _n_s_h_p_o_p_e_n should be closed by _n_s_h_p_c_l_o_s_e,
     which waits for the associated process to terminate and
     returns the exit status of the command.

     Because open files are shared, a type "r" command may be
     used as an input filter, and a type "w" as an output filter.

     _N_s_h_p_o_p_e_n breaks up the _c_o_m_m_a_n_d argument string at spaces and
     tabs for the child process.  However, it does not invoke a
     shell, and does not attempt any shell shell meta character
     parsing.  In particular, quoted white space will still cause
     argument seperation.  By avoiding calling a shell, pipe
     creation is a great deal quicker.  Also, by avoiding the
     (rather complicated) shell meta character parsing, some
     types of bugs may be avoided.  This is important where the
     security of setuid programs is involved.

SEE ALSO
     pipe(2), popen(3), fopen(3S), fclose(3S), system(3),
     wait(2), sh(1)

DIAGNOSTICS
     _N_s_h_p_o_p_e_n returns a null pointer if files or processes cannot
     be created, or the shell cannot be accessed.

     _N_s_h_p_c_l_o_s_e returns -1 if _s_t_r_e_a_m is not associated with an
     `nshpopened' command.

BUGS
     Buffered reading before opening an input filter may leave
     the standard input of that filter mispositioned.  Similar



Printed 5/16/88               local                             1






NSHPOPEN(3)         UNIX Programmer's Manual          NSHPOPEN(3)



     problems with an output filter may be forestalled by careful
     buffer flushing, for instance, with _f_f_l_u_s_h, see _f_c_l_o_s_e(3).

     _N_s_h_p_o_p_e_n does not call a shell to do it's work.  It does not
     attempt to process shell meta characters.  Thus, it does not
     treat quotes, I/O redirects, or file name wildcard charac-
     ters specially.  This is it's incompatibility with _p_o_p_e_n(_3).

     This type of function should have been included with
     _p_o_p_e_n(_3) in the standard I/O library.













































Printed 5/16/88               local                             2