explain_execve(3)

🎀 explain_execve — the girl who explains why ur execve(2) said no (NAME)

okay bestie, sit down, hydrate, because we're doing the explain_execve(3) page of the Library Functions Manual and it's genuinely so useful it's giving main character energy. ✨

Here's the vibe: you called execve(2), it returned an error, and now you're just standing there holding a raw errno like it's a cryptic text from a crush. 🙈 These functions take that error and hand you back an actual explanation. No cap.

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✨ SYNOPSIS ✨

#include <libexplain/execve.h>
const char *explain_execve(const char *pathname, const char *const
*argv, const char *const *envp);
const char *explain_errno_execve(int errnum, const char *pathname, const
char *const *argv, const char *const *envp);
void explain_message_execve(char *message, int message_size, const char
*pathname, const char *const *argv, const char *const *envp);
void explain_message_errno_execve(char *message, int message_size, int
errnum, const char *pathname, const char *const *argv, const char *const
*envp);

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🌸 DESCRIPTION 🌸

So like, these functions may be used to obtain explanations for errors returned by the execve(2) system call. That's the whole assignment. 🫶

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💖 explain_execve

const char *explain_execve(const char *pathname, const char *const
*argv, const char *const *envp);

The explain_execve function is used to obtain an explanation of an error returned by the execve(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail. Like, it actually tells you what happened. Iconic.

The errno global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:

execve(pathname, argv, envp);
fprintf(stderr, "%s\n", explain_execve(pathname, argv, envp));
exit(EXIT_FAILURE);

• pathname — the original pathname, exactly as passed to the execve(2) system call. Don't get cute and re-derive it, bestie, pass the og. 💅
• argv — the original argv, exactly as passed to the execve(2) system call.
• envp — the original envp, exactly as passed to the execve(2) system call.

Returns:

The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads. 😭

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. Yeah. It's a group project buffer and everyone's editing the same doc.

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🦋 explain_errno_execve

const char *explain_errno_execve(int errnum, const char *pathname, const
char *const *argv, const char *const *envp);

The explain_errno_execve function is used to obtain an explanation of an error returned by the execve(2) system call. The least the message will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail. She's thorough. 🎀

This function is intended to be used in a fashion similar to the following example:

execve(pathname, argv, envp);
int err = errno;
fprintf(stderr, "%s\n", explain_errno_execve(err, pathname, argv, envp));
exit(EXIT_FAILURE);

• errnum — the error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno. 🚨 (Translation: grab errno first, then do stuff, then explain. Otherwise the number you're explaining belongs to somebody else entirely.)
• pathname — the original pathname, exactly as passed to the execve(2) system call.
• argv — the original argv, exactly as passed to the execve(2) system call.
• envp — the original envp, exactly as passed to the execve(2) system call.

Returns:

The message explaining the error. This message buffer is shared by all libexplain functions which do not supply a buffer in their argument list. This will be overwritten by the next call to any libexplain function which shares this buffer, including other threads.

Note: This function is not thread safe, because it shares a return buffer across all threads, and many other functions in this library. Same shared-buffer drama as before, different function name. 💀

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🌈 explain_message_execve

void explain_message_execve(char *message, int message_size, const char
*pathname, const char *const *argv, const char *const *envp);

The explain_message_execve function may be used to obtain an explanation of an error returned by the execve(2) system call. The least the message will contain is the value of strerror(errno), but usually it will do much better, and indicate the underlying cause in more detail.

The errno global variable will be used to obtain the error value to be decoded.

This function is intended to be used in a fashion similar to the following example:

execve(pathname, argv, envp);
char message[3000];
explain_message_execve(message, sizeof(message), pathname, argv, envp);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);

• message — the location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe. 🎉 (see? we fixed it. growth.)
• message_size — the size in bytes of the location in which to store the returned message.
• pathname — the original pathname, exactly as passed to the execve(2) system call.
• argv — the original argv, exactly as passed to the execve(2) system call.
• envp — the original envp, exactly as passed to the execve(2) system call.

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🧚 explain_message_errno_execve

void explain_message_errno_execve(char *message, int message_size, int
errnum, const char *pathname, const char *const *argv, const char *const
*envp);

The explain_message_errno_execve function may be used to obtain an explanation of an error returned by the execve(2) system call. The least the message will contain is the value of strerror(errnum), but usually it will do much better, and indicate the underlying cause in more detail.

This function is intended to be used in a fashion similar to the following example:

execve(pathname, argv, envp);
int err = errno;
char message[3000];
explain_message_errno_execve(message, sizeof(message), err,
    pathname, argv, envp);
fprintf(stderr, "%s\n", message);
exit(EXIT_FAILURE);

• message — the location in which to store the returned message. If a suitable message return buffer is supplied, this function is thread safe. 💅
• message_size — the size in bytes of the location in which to store the returned message.
• errnum — the error value to be decoded, usually obtained from the errno global variable just before this function is called. This is necessary if you need to call any code between the system call to be explained and this function, because many libc functions will alter the value of errno. (Yes we said this already but it matters, ok? 🫶)
• pathname — the original pathname, exactly as passed to the execve(2) system call.
• argv — the original argv, exactly as passed to the execve(2) system call.
• envp — the original envp, exactly as passed to the execve(2) system call.

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👑 SEE ALSO 👑

• execve(2) — execute program
• explain_execve_or_die(3) — execute program and report errors

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💜 COPYRIGHT 💜

libexplain version 1.4 Copyright (C) 2008 Peter Miller

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ok that's the whole page bestie, go forth and explain ur errors, you ate. 🍓✨ And for the record? This whole explain_execve(3) page is libexplain version 1.4, copyright (C) 2008 Peter Miller — shoutout to Peter, fr fr. 💖 No cap, that's a wrap. 🎀🦋