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Full Discussion: question about popen in C
Top Forums Programming question about popen in C Post 302505010 by omega666 on Wednesday 16th of March 2011 01:06:43 AM
Old 03-16-2011
so if i set an element of a file_pointer array to 0, and then i compare NULL to that value 0, will it crash or just result to false, cause i set the file pointer array and pid array to 0, after closing its respective file pointer. this is like removing the struct from the chain of structs, but using an array method.

also
for the popen_new function
the instruction given was ls; ls

Last edited by omega666; 03-17-2011 at 05:15 PM..
 

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scandir(3)						     Library Functions Manual							scandir(3)

NAME
scandir, alphasort - Scans or sorts directory contents LIBRARY
Standard C Library (libc.a) SYNOPSIS
#include <sys/types.h> #include <sys/dir.h> int scandir ( char *dir_name, struct dirent * (*name_list[ ]), int (*select) ( struct dirent *dir ), int (*compare) ( struct dirent **dir1, struct dirent **dir2 ) ); int alphasort ( struct dirent **dir1, struct dirent **dir2 ); PARAMETERS
Points to the directory name. Points to the array of pointers to directory entries. Points to a user-supplied function that is called by the scandir() function to select which entries to include in the array. Points to a user-supplied function that sorts the completed array. Points to a dirent structure. Points to a dirent structure. DESCRIPTION
The scandir() function reads the directory pointed to by the dir_name parameter. It then uses the malloc() function to create an array of pointers to directory entries. The scandir() function returns the number of entries in the array and, through the name_list parameter, a pointer to the array. The select parameter points to a user-supplied function that the scandir() function calls to select which entries to include in the array. The selection routine is passed a pointer to a directory entry and returns a nonzero value for a directory entry that is included in the array. If the select parameter is a null value, all directory entries are included. The compare parameter points to a user-supplied function that is passed to the qsort() function to sort the completed array. If the compare parameter is a null value, the array is not sorted. The memory allocated to the array can be deallocated by freeing each pointer in the array, and the array itself, with the free() function. The alphasort() function alphabetically compares the two dirent structures pointed to by the dir1 and dir2 parameters. This function can be passed as the compare parameter to either the scandir() function or the qsort() function. A user-supplied subroutine may also be used. RETURN VALUES
The scandir() function returns -1 if the directory cannot be opened for reading or if the malloc() function cannot allocate enough memory to hold all the data structures. If successful, the scandir() function returns the number of entries found. The alphasort() function returns the following values: Less than 0 (zero): The dirent structure pointed to by the dir1 parameter is lexi- cally less than the dirent structure pointed to by the dir2 parameter. 0 (zero): The dirent structures pointed to by the dir1 parameter and the dir2 parameter are equal. Greater than 0 (zero): The dirent structure pointed to by the dir1 parameter is lexically greater than the dirent structure pointed to by the dir2 parameter. RELATED INFORMATION
Functions: malloc(3), opendir(3), qsort(3) delim off scandir(3)
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