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terminal-util: add CLEANUP_TERMIOS_RESET() for automatic termios restore

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Add TERMIOS_NULL sentinel, TermiosResetContext, and CLEANUP_TERMIOS_RESET()
macro (modeled after CLEANUP_ARRAY()) to automatically restore terminal
settings when leaving scope, replacing manual goto+tcsetattr patterns.

Migrate ask_string_full(), terminal_get_cursor_position(),
get_default_background_color(), terminal_get_terminfo_by_dcs(),
terminal_get_size_by_dsr() and terminal_get_size_by_csi18() to use the new
cleanup macro, removing the goto-based cleanup labels and replacing them
with direct returns.

Co-developed-by: Claude Opus 4.6 <noreply@anthropic.com>
This commit is contained in:
Daan De Meyer
2026-03-31 14:42:02 +02:00
committed by Daan De Meyer
parent 138c08d803
commit 9fc49a4ca7
2 changed files with 119 additions and 124 deletions
Download Patch File Download Diff File Expand all files Collapse all files
src/basic/terminal-util.c
+96 -124
View File
@@ -309,13 +309,17 @@ int ask_string_full(
* swapping out stdin/stdout. */
int fd_input = fileno(stdin);
int fd_output = fileno(stdout);
struct termios old_termios = TERMIOS_NULL;
CLEANUP_TERMIOS_RESET(fd_input, old_termios);
if (fd_input < 0 || fd_output < 0 || same_fd(fd_input, fd_output) <= 0)
goto fallback;
/* Try to disable echo, which also tells us if this even is a terminal */
struct termios old_termios;
if (tcgetattr(fd_input, &old_termios) < 0)
if (tcgetattr(fd_input, &old_termios) < 0) {
old_termios = TERMIOS_NULL;
goto fallback;
}
struct termios new_termios = old_termios;
termios_disable_echo(&new_termios);
@@ -342,15 +346,13 @@ int ask_string_full(
if (get_completions) {
r = get_completions(string, &completions, userdata);
if (r < 0)
goto fail;
return r;
}
_cleanup_free_ char *new_string = NULL;
CompletionResult cr = pick_completion(string, completions, &new_string);
if (cr < 0) {
r = cr;
goto fail;
}
if (cr < 0)
return cr;
if (IN_SET(cr, COMPLETION_PARTIAL, COMPLETION_FULL)) {
/* Output the new suffix we learned */
fputs(ASSERT_PTR(startswith(new_string, strempty(string))), stdout);
@@ -369,10 +371,8 @@ int ask_string_full(
fputc('\n', stdout);
_cleanup_strv_free_ char **filtered = strv_filter_prefix(completions, string);
if (!filtered) {
r = -ENOMEM;
goto fail;
}
if (!filtered)
return -ENOMEM;
r = show_menu(filtered,
/* n_columns= */ SIZE_MAX,
@@ -381,7 +381,7 @@ int ask_string_full(
/* grey_prefix= */ string,
/* with_numbers= */ false);
if (r < 0)
goto fail;
return r;
/* Show the prompt again */
fputs(ansi_highlight(), stdout);
@@ -419,8 +419,7 @@ int ask_string_full(
} else if (c == 4) {
/* Ctrl-d → cancel this field input */
r = -ECANCELED;
goto fail;
return -ECANCELED;
} else if (char_is_cc(c) || n >= LINE_MAX)
/* refuse control characters and too long strings */
@@ -428,10 +427,8 @@ int ask_string_full(
else {
/* Regular char */
if (!GREEDY_REALLOC(string, n+2)) {
r = -ENOMEM;
goto fail;
}
if (!GREEDY_REALLOC(string, n+2))
return -ENOMEM;
string[n++] = (char) c;
string[n] = 0;
@@ -442,9 +439,6 @@ int ask_string_full(
fflush(stdout);
}
if (tcsetattr(fd_input, TCSANOW, &old_termios) < 0)
return -errno;
if (!string) {
string = strdup("");
if (!string)
@@ -454,10 +448,6 @@ int ask_string_full(
*ret = TAKE_PTR(string);
return 0;
fail:
(void) tcsetattr(fd_input, TCSANOW, &old_termios);
return r;
fallback:
/* A simple fallback without TTY magic */
r = read_line(stdin, LONG_LINE_MAX, &string);
@@ -1993,7 +1983,11 @@ int terminal_get_cursor_position(
if (r < 0)
return log_debug_errno(r, "Called with distinct input/output fds: %m");
struct termios old_termios;
/* Failure to reset the terminal is ignored here and in similar cases below.
* We already have our result; if cleanup fails it doesn't change the validity of the result. */
struct termios old_termios = TERMIOS_NULL;
CLEANUP_TERMIOS_RESET(input_fd, old_termios);
if (tcgetattr(input_fd, &old_termios) < 0)
return log_debug_errno(errno, "Failed to get terminal settings: %m");
@@ -2006,14 +2000,14 @@ int terminal_get_cursor_position(
/* Request cursor position (DSR/CPR) */
r = loop_write(output_fd, "\x1B[6n", SIZE_MAX);
if (r < 0)
goto finish;
return r;
/* Open a 2nd input fd, in non-blocking mode, so that we won't ever hang in read() should someone
* else process the POLLIN. */
nonblock_input_fd = r = fd_reopen(input_fd, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
if (r < 0)
goto finish;
return r;
usec_t end = usec_add(now(CLOCK_MONOTONIC), CONSOLE_REPLY_WAIT_USEC);
char buf[STRLEN("\x1B[1;1R")]; /* The shortest valid reply possible */
@@ -2023,18 +2017,14 @@ int terminal_get_cursor_position(
for (bool first = true;; first = false) {
if (buf_full == 0) {
usec_t n = now(CLOCK_MONOTONIC);
if (n >= end) {
r = -EOPNOTSUPP;
goto finish;
}
if (n >= end)
return -EOPNOTSUPP;
r = fd_wait_for_event(nonblock_input_fd, POLLIN, usec_sub_unsigned(end, n));
if (r < 0)
goto finish;
if (r == 0) {
r = -EOPNOTSUPP;
goto finish;
}
return r;
if (r == 0)
return -EOPNOTSUPP;
/* On the first try, read multiple characters, i.e. the shortest valid
* reply. Afterwards read byte-wise, since we don't want to read too much, and
@@ -2044,8 +2034,7 @@ int terminal_get_cursor_position(
if (errno == EAGAIN)
continue;
r = -errno;
goto finish;
return -errno;
}
assert((size_t) l <= sizeof(buf));
@@ -2055,7 +2044,7 @@ int terminal_get_cursor_position(
size_t processed;
r = scan_cursor_position_response(&context, buf, buf_full, &processed);
if (r < 0)
goto finish;
return r;
assert(processed <= buf_full);
buf_full -= processed;
@@ -2063,26 +2052,17 @@ int terminal_get_cursor_position(
if (r > 0) {
/* Superficial validity check */
if (context.row >= 32766 || context.column >= 32766) {
r = -ENODATA;
goto finish;
}
if (context.row >= 32766 || context.column >= 32766)
return -ENODATA;
if (ret_row)
*ret_row = context.row;
if (ret_column)
*ret_column = context.column;
r = 0;
goto finish;
return 0;
}
}
finish:
/* We ignore failure here and in similar cases below. We already got a reply and if cleanup fails,
* this doesn't change the validity of the result. */
(void) tcsetattr(input_fd, TCSANOW, &old_termios);
return r;
}
int terminal_reset_defensive(int fd, TerminalResetFlags flags) {
@@ -2124,6 +2104,23 @@ void termios_disable_echo(struct termios *termios) {
termios->c_cc[VTIME] = 0;
}
static bool termios_is_null(const struct termios *t) {
if (!t)
return true;
return t->c_iflag == UINT_MAX &&
t->c_oflag == UINT_MAX &&
t->c_cflag == UINT_MAX &&
t->c_lflag == UINT_MAX;
}
void termios_reset(const TermiosResetContext *c) {
assert(c);
if (c->fd && *c->fd >= 0 && !termios_is_null(c->termios))
(void) tcsetattr(*c->fd, TCSANOW, c->termios);
}
typedef enum BackgroundColorState {
BACKGROUND_TEXT,
BACKGROUND_ESCAPE,
@@ -2295,7 +2292,9 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
if (r < 0)
return r;
struct termios old_termios;
struct termios old_termios = TERMIOS_NULL;
CLEANUP_TERMIOS_RESET(nonblock_input_fd, old_termios);
if (tcgetattr(nonblock_input_fd, &old_termios) < 0)
return -errno;
@@ -2307,7 +2306,7 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
r = loop_write(STDOUT_FILENO, ANSI_OSC "11;?" ANSI_ST, SIZE_MAX);
if (r < 0)
goto finish;
return r;
usec_t end = usec_add(now(CLOCK_MONOTONIC), CONSOLE_REPLY_WAIT_USEC);
char buf[STRLEN(ANSI_OSC "11;rgb:0/0/0" ANSI_ST)]; /* shortest possible reply */
@@ -2317,18 +2316,14 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
for (bool first = true;; first = false) {
if (buf_full == 0) {
usec_t n = now(CLOCK_MONOTONIC);
if (n >= end) {
r = -EOPNOTSUPP;
goto finish;
}
if (n >= end)
return -EOPNOTSUPP;
r = fd_wait_for_event(nonblock_input_fd, POLLIN, usec_sub_unsigned(end, n));
if (r < 0)
goto finish;
if (r == 0) {
r = -EOPNOTSUPP;
goto finish;
}
return r;
if (r == 0)
return -EOPNOTSUPP;
/* On the first try, read multiple characters, i.e. the shortest valid
* reply. Afterwards read byte-wise, since we don't want to read too much, and
@@ -2337,8 +2332,7 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
if (l < 0) {
if (errno == EAGAIN)
continue;
r = -errno;
goto finish;
return -errno;
}
assert((size_t) l <= sizeof(buf));
@@ -2348,7 +2342,7 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
size_t processed;
r = scan_background_color_response(&context, buf, buf_full, &processed);
if (r < 0)
goto finish;
return r;
assert(processed <= buf_full);
buf_full -= processed;
@@ -2361,14 +2355,9 @@ int get_default_background_color(double *ret_red, double *ret_green, double *ret
*ret_green = (double) context.green / ((UINT64_C(1) << context.green_bits) - 1);
assert(context.blue_bits > 0);
*ret_blue = (double) context.blue / ((UINT64_C(1) << context.blue_bits) - 1);
r = 0;
goto finish;
return 0;
}
}
finish:
(void) tcsetattr(nonblock_input_fd, TCSANOW, &old_termios);
return r;
}
int terminal_get_size_by_dsr(
@@ -2405,7 +2394,9 @@ int terminal_get_size_by_dsr(
if (r < 0)
return r;
struct termios old_termios;
struct termios old_termios = TERMIOS_NULL;
CLEANUP_TERMIOS_RESET(nonblock_input_fd, old_termios);
if (tcgetattr(nonblock_input_fd, &old_termios) < 0)
return log_debug_errno(errno, "Failed to get terminal settings: %m");
@@ -2516,7 +2507,6 @@ finish:
/* Restore cursor position */
if (saved_row > 0 && saved_column > 0)
(void) terminal_set_cursor_position(output_fd, saved_row, saved_column);
(void) tcsetattr(nonblock_input_fd, TCSANOW, &old_termios);
return r;
}
@@ -2582,7 +2572,9 @@ int terminal_get_size_by_csi18(
if (r < 0)
return r;
struct termios old_termios;
struct termios old_termios = TERMIOS_NULL;
CLEANUP_TERMIOS_RESET(nonblock_input_fd, old_termios);
if (tcgetattr(nonblock_input_fd, &old_termios) < 0)
return log_debug_errno(errno, "Failed to get terminal settings: %m");
@@ -2594,7 +2586,7 @@ int terminal_get_size_by_csi18(
r = loop_write(output_fd, CSI18_Q, SIZE_MAX);
if (r < 0)
goto finish;
return r;
usec_t end = usec_add(now(CLOCK_MONOTONIC), CONSOLE_REPLY_WAIT_USEC);
char buf[STRLEN(CSI18_R1)];
@@ -2602,18 +2594,14 @@ int terminal_get_size_by_csi18(
for (;;) {
usec_t n = now(CLOCK_MONOTONIC);
if (n >= end) {
r = -EOPNOTSUPP;
break;
}
if (n >= end)
return -EOPNOTSUPP;
r = fd_wait_for_event(nonblock_input_fd, POLLIN, usec_sub_unsigned(end, n));
if (r < 0)
break;
if (r == 0) {
r = -EOPNOTSUPP;
break;
}
return r;
if (r == 0)
return -EOPNOTSUPP;
/* On the first read, read multiple characters, i.e. the shortest valid reply. Afterwards
* read byte by byte, since we don't want to read too much and drop characters from the input
@@ -2622,8 +2610,7 @@ int terminal_get_size_by_csi18(
if (l < 0) {
if (errno == EAGAIN)
continue;
r = -errno;
break;
return -errno;
}
assert((size_t) l <= sizeof(buf) - bytes);
@@ -2631,20 +2618,14 @@ int terminal_get_size_by_csi18(
r = scan_text_area_size_response(buf, bytes, ret_rows, ret_columns);
if (r != -EAGAIN)
break;
return r;
if (bytes == sizeof(buf)) {
r = -EOPNOTSUPP; /* The response has the right prefix, but we didn't find a valid
* answer with a terminator in the allotted space. Something is
* wrong, possibly some unrelated bytes got injected into the
* answer. */
break;
}
if (bytes == sizeof(buf))
return -EOPNOTSUPP; /* The response has the right prefix, but we didn't find a valid
* answer with a terminator in the allotted space. Something is
* wrong, possibly some unrelated bytes got injected into the
* answer. */
}
finish:
(void) tcsetattr(nonblock_input_fd, TCSANOW, &old_termios);
return r;
}
int terminal_fix_size(int input_fd, int output_fd) {
@@ -2745,7 +2726,9 @@ int terminal_get_terminfo_by_dcs(int fd, char **ret_name) {
/* Note: fd must be in non-blocking read-write mode! */
struct termios old_termios;
struct termios old_termios = TERMIOS_NULL;
CLEANUP_TERMIOS_RESET(fd, old_termios);
if (tcgetattr(fd, &old_termios) < 0)
return -errno;
@@ -2757,7 +2740,7 @@ int terminal_get_terminfo_by_dcs(int fd, char **ret_name) {
r = loop_write(fd, DCS_TERMINFO_Q, SIZE_MAX);
if (r < 0)
goto finish;
return r;
usec_t end = usec_add(now(CLOCK_MONOTONIC), CONSOLE_REPLY_WAIT_USEC);
char buf[STRLEN(DCS_TERMINFO_R1) + MAX_TERMINFO_LENGTH + STRLEN(ANSI_ST)];
@@ -2765,18 +2748,14 @@ int terminal_get_terminfo_by_dcs(int fd, char **ret_name) {
for (;;) {
usec_t n = now(CLOCK_MONOTONIC);
if (n >= end) {
r = -EOPNOTSUPP;
break;
}
if (n >= end)
return -EOPNOTSUPP;
r = fd_wait_for_event(fd, POLLIN, usec_sub_unsigned(end, n));
if (r < 0)
break;
if (r == 0) {
r = -EOPNOTSUPP;
break;
}
return r;
if (r == 0)
return -EOPNOTSUPP;
/* On the first read, read multiple characters, i.e. the shortest valid reply. Afterwards
* read byte by byte, since we don't want to read too much and drop characters from the input
@@ -2785,8 +2764,7 @@ int terminal_get_terminfo_by_dcs(int fd, char **ret_name) {
if (l < 0) {
if (errno == EAGAIN)
continue;
r = -errno;
break;
return -errno;
}
assert((size_t) l <= sizeof(buf) - bytes);
@@ -2794,20 +2772,14 @@ int terminal_get_terminfo_by_dcs(int fd, char **ret_name) {
r = scan_terminfo_response(buf, bytes, ret_name);
if (r != -EAGAIN)
break;
return r;
if (bytes == sizeof(buf)) {
r = -EOPNOTSUPP; /* The response has the right prefix, but we didn't find a valid
* answer with a terminator in the allotted space. Something is
* wrong, possibly some unrelated bytes got injected into the
* answer. */
break;
}
if (bytes == sizeof(buf))
return -EOPNOTSUPP; /* The response has the right prefix, but we didn't find a valid
* answer with a terminator in the allotted space. Something is
* wrong, possibly some unrelated bytes got injected into the
* answer. */
}
finish:
(void) tcsetattr(fd, TCSANOW, &old_termios);
return r;
}
int have_terminfo_file(const char *name) {
src/basic/terminal-util.h
+23
View File
@@ -145,6 +145,29 @@ assert_cc((TTY_MODE & 0711) == 0600);
void termios_disable_echo(struct termios *termios);
/* A termios sentinel with all flag fields set to all-ones-bits. No real tcgetattr() result will ever
* match this because the multi-bit sub-fields (CSIZE, CBAUD, …) can't validly have every bit set. */
#define TERMIOS_NULL (struct termios) { \
.c_iflag = UINT_MAX, \
.c_oflag = UINT_MAX, \
.c_cflag = UINT_MAX, \
.c_lflag = UINT_MAX, \
}
typedef struct TermiosResetContext {
int *fd;
struct termios *termios;
} TermiosResetContext;
void termios_reset(const TermiosResetContext *c);
#define CLEANUP_TERMIOS_RESET(_fd, _termios) \
_cleanup_(termios_reset) _unused_ const TermiosResetContext \
CONCATENATE(_cleanup_termios_, UNIQ) = { \
.fd = &(_fd), \
.termios = &(_termios), \
}
/* The $TERM value we use for terminals other than the Linux console */
#define FALLBACK_TERM "vt220"