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Shell: Implement a very basic exec builtin

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Other shells also support a number of other options with exec and
some have special behaviour when calling exec with no arguments except
redirections.

This PR only supports the basic case of replacing the Shell process
(or LibShell host process) with the provided command.
This commit is contained in:
William Marlow
2020-12-29 19:42:34 +00:00
committed by Andreas Kling
parent 50d24e4f98
commit 96cd04f2ba
3 changed files with 59 additions and 36 deletions
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78
Shell/Shell.cpp
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@@ -789,42 +789,7 @@ RefPtr<Job> Shell::run_command(const AST::Command& command)
// We no longer need the jobs here.
jobs.clear();
int rc = execvp(argv[0], const_cast<char* const*>(argv.data()));
if (rc < 0) {
int saved_errno = errno;
struct stat st;
if (stat(argv[0], &st)) {
fprintf(stderr, "stat(%s): %s\n", argv[0], strerror(errno));
_exit(126);
}
if (!(st.st_mode & S_IXUSR)) {
fprintf(stderr, "%s: Not executable\n", argv[0]);
_exit(126);
}
if (saved_errno == ENOENT) {
int shebang_fd = open(argv[0], O_RDONLY);
auto close_argv = ScopeGuard([shebang_fd]() { if (shebang_fd >= 0) close(shebang_fd); });
char shebang[256] {};
ssize_t num_read = -1;
if ((shebang_fd >= 0) && ((num_read = read(shebang_fd, shebang, sizeof(shebang))) >= 2) && (StringView(shebang).starts_with("#!"))) {
StringView shebang_path_view(&shebang[2], num_read - 2);
Optional<size_t> newline_pos = shebang_path_view.find_first_of("\n\r");
shebang[newline_pos.has_value() ? (newline_pos.value() + 2) : num_read] = '\0';
argv[0] = shebang;
int rc = execvp(argv[0], const_cast<char* const*>(argv.data()));
if (rc < 0)
fprintf(stderr, "%s: Invalid interpreter \"%s\": %s\n", argv[0], &shebang[2], strerror(errno));
} else
fprintf(stderr, "%s: Command not found.\n", argv[0]);
} else {
if (S_ISDIR(st.st_mode)) {
fprintf(stderr, "Shell: %s: Is a directory\n", argv[0]);
_exit(126);
}
fprintf(stderr, "execvp(%s): %s\n", argv[0], strerror(saved_errno));
}
_exit(126);
}
execute_process(move(argv));
ASSERT_NOT_REACHED();
}
@@ -893,6 +858,47 @@ RefPtr<Job> Shell::run_command(const AST::Command& command)
return *job;
}
void Shell::execute_process(Vector<const char*>&& argv)
{
int rc = execvp(argv[0], const_cast<char* const*>(argv.data()));
if (rc < 0) {
int saved_errno = errno;
struct stat st;
if (stat(argv[0], &st)) {
fprintf(stderr, "stat(%s): %s\n", argv[0], strerror(errno));
_exit(126);
}
if (!(st.st_mode & S_IXUSR)) {
fprintf(stderr, "%s: Not executable\n", argv[0]);
_exit(126);
}
if (saved_errno == ENOENT) {
int shebang_fd = open(argv[0], O_RDONLY);
auto close_argv = ScopeGuard([shebang_fd]() { if (shebang_fd >= 0) close(shebang_fd); });
char shebang[256] {};
ssize_t num_read = -1;
if ((shebang_fd >= 0) && ((num_read = read(shebang_fd, shebang, sizeof(shebang))) >= 2) && (StringView(shebang).starts_with("#!"))) {
StringView shebang_path_view(&shebang[2], num_read - 2);
Optional<size_t> newline_pos = shebang_path_view.find_first_of("\n\r");
shebang[newline_pos.has_value() ? (newline_pos.value() + 2) : num_read] = '\0';
argv[0] = shebang;
int rc = execvp(argv[0], const_cast<char* const*>(argv.data()));
if (rc < 0)
fprintf(stderr, "%s: Invalid interpreter \"%s\": %s\n", argv[0], &shebang[2], strerror(errno));
} else
fprintf(stderr, "%s: Command not found.\n", argv[0]);
} else {
if (S_ISDIR(st.st_mode)) {
fprintf(stderr, "Shell: %s: Is a directory\n", argv[0]);
_exit(126);
}
fprintf(stderr, "execvp(%s): %s\n", argv[0], strerror(saved_errno));
}
_exit(126);
}
ASSERT_NOT_REACHED();
}
void Shell::run_tail(const AST::Command& invoking_command, const AST::NodeWithAction& next_in_chain, int head_exit_code)
{
if (m_error != ShellError::None) {