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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
Notes: sideshowbarker 2024-07-19 17:30:42 +09:00 
Author: https://github.com/lux01
Commit: https://github.com/SerenityOS/serenity/commit/96cd04f2ba4
Pull-request: https://github.com/SerenityOS/serenity/pull/4638
3 changed files with 59 additions and 36 deletions
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14
Shell/Builtin.cpp
View File

@ -256,6 +256,20 @@ int Shell::builtin_dirs(int argc, const char** argv)
return 0;
}
int Shell::builtin_exec(int argc, const char** argv)
{
if (argc < 2) {
fprintf(stderr, "Shell: No command given to exec\n");
return 1;
}
Vector<const char*> argv_vector;
argv_vector.append(argv + 1, argc - 1);
argv_vector.append(nullptr);
execute_process(move(argv_vector));
}
int Shell::builtin_exit(int argc, const char** argv)
{
int exit_code = 0;

78
Shell/Shell.cpp
View File

@ -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) {

3
Shell/Shell.h
View File

@ -45,6 +45,7 @@
__ENUMERATE_SHELL_BUILTIN(cd) \
__ENUMERATE_SHELL_BUILTIN(cdh) \
__ENUMERATE_SHELL_BUILTIN(pwd) \
__ENUMERATE_SHELL_BUILTIN(exec) \
__ENUMERATE_SHELL_BUILTIN(exit) \
__ENUMERATE_SHELL_BUILTIN(export) \
__ENUMERATE_SHELL_BUILTIN(glob) \
@ -253,6 +254,8 @@ private:
void run_tail(RefPtr<Job>);
void run_tail(const AST::Command&, const AST::NodeWithAction&, int head_exit_code);
[[noreturn]] void execute_process(Vector<const char*>&& argv);
virtual void custom_event(Core::CustomEvent&) override;
#define __ENUMERATE_SHELL_BUILTIN(builtin) \