Question

I compile a C library on mac os x. When I typed the input and after printing on the screen the data I don’t see something.

char *path = NULL;
peerdisplay = "Bob";
printf("Insert the full 'To' path: ");
scanf(" %a[^\n]", &path);
printf("A path: %s \n", &path);

When I replace the %a to %s, the printing ok, but after the running I have a segmentation error.
I like to running such as script.

Answer 1

%a is gnu-specific non-standard extension to scanf grabs. What says your OS X manpages about it ?

The GNU C library supports a non-standard extension that causes the
library to dynamically allocate a string of sufficient size for input
strings for the %s and %a[range] conversion specifiers. To make use
of this feature, specify a as a length modifier (thus %as or
%a[range]). The caller must free(3) the returned string

^is that your intent ?

in that case, be aware that

The a modifier is not available if the program is compiled with gcc
-std=c99 or gcc -D_ISOC99_SOURCE (unless _GNU_SOURCE is also speci-
fied), in which case the a is interpreted as a specifier for floating-
point numbers (see above).