PREROOT(3)

okay so bestie, welcome to PREROOT(3) from the Library Functions Manual — the page about preroot support, and yes we’re gonna get into all of it 💖

🌸 NAME 🌸

preroot — preroot support, aka the whole per-process root situation. periodt.

✨ SYNOPSIS ✨

#include <preroot.h>

char*    getpreroot(char* path, char* cmd);
int      ispreroot(char* dir);
int      realopen(char* path, int mode, int perm);
void     setpreroot(char** argv, char* dir);

🦋 DESCRIPTION 🦋

okay so the preroot routines manipulate the process preroot. and what is preroot? it’s a kernel supported per-process two level viewpath. literally all pathnames rooted at / are first searched for in the process preroot directory and then in the system root directory. setting the process preroot is a privileged operation controlled by the /etc/preroot(1) command. slay.

<preroot.h> defines the symbol FS_PREROOT for those systems that support preroot. the following routines are valid only when FS_PREROOT is defined:

• getpreroot — returns a pointer to the absolute pathname of the preroot directory for the executable cmd. the result is placed in path. if path is 0, then malloc(3) is used to allocate the pathname space. 0 is returned if cmd has no preroot or if an error was encountered. in that case, errno is set to indicate the error. no cap.
• ispreroot — non-zero is returned if dir is the current process preroot. if dir is 0, then non-zero is returned if the current process has a preroot. vibe check: zero means no, nonzero means yes.
• realopen — temporarily disables the process preroot and does an open(3) relative to the system root directory. the return value from open is returned. if there is no preroot, then realopen is equivalent to open. iconic.
• setpreroot — calls execvp(3) as execvp(argv[0],argv) with the process preroot set to dir. argv must be a 0-terminated argument array. if argv is 0, then the value of opt_argv from optget(3) is used. setpreroot returns immediately if dir is already the process preroot. she’s efficient, okay?

👑 SEE ALSO 👑

• /etc/preroot(1)

💀 BUGS 💀

preroot semantics should be preserved when reading directories. the ast directory(3) routines do this. 3d(1) viewpathing does preroot the right way.

okay bye bestie — this was the PREROOT(3) page from the Library Functions Manual, and there’s no extra version/date footer text beyond that, so that’s the whole thing. stay rooted 💅✨