journalctl: allow --lines=0 i.e. only new

Makes it easier to watch just for new entries. Once scenario
is where the user starts 'journalctl -qfn0' to watch for changes
during some operation.
parent 390b5e55
......@@ -60,7 +60,7 @@ static bool arg_follow = false;
static bool arg_full = false;
static bool arg_all = false;
static bool arg_no_pager = false;
static unsigned arg_lines = 0;
static int arg_lines = -1;
static bool arg_no_tail = false;
static bool arg_quiet = false;
static bool arg_merge = false;
......@@ -239,8 +239,8 @@ static int parse_argv(int argc, char *argv[]) {
case 'n':
if (optarg) {
r = safe_atou(optarg, &arg_lines);
if (r < 0 || arg_lines <= 0) {
r = safe_atoi(optarg, &arg_lines);
if (r < 0 || arg_lines < 0) {
log_error("Failed to parse lines '%s'", optarg);
return -EINVAL;
}
......@@ -413,7 +413,7 @@ static int parse_argv(int argc, char *argv[]) {
}
}
if (arg_follow && !arg_no_tail && arg_lines <= 0)
if (arg_follow && !arg_no_tail && arg_lines < 0)
arg_lines = 10;
if (arg_since_set && arg_until_set && arg_since_set > arg_until_set) {
......@@ -849,8 +849,8 @@ int main(int argc, char *argv[]) {
sd_journal *j = NULL;
bool need_seek = false;
sd_id128_t previous_boot_id;
bool previous_boot_id_valid = false;
unsigned n_shown = 0;
bool previous_boot_id_valid = false, first_line = true;
int n_shown = 0;
setlocale(LC_ALL, "");
log_parse_environment();
......@@ -937,6 +937,11 @@ int main(int argc, char *argv[]) {
if (r < 0)
goto finish;
/* Opening the fd now means the first sd_journal_wait() will actually wait */
r = sd_journal_get_fd(j);
if (r < 0)
goto finish;
if (arg_field) {
const void *data;
size_t size;
......@@ -950,7 +955,7 @@ int main(int argc, char *argv[]) {
SD_JOURNAL_FOREACH_UNIQUE(j, data, size) {
const void *eq;
if (arg_lines > 0 && n_shown >= arg_lines)
if (arg_lines >= 0 && n_shown >= arg_lines)
break;
eq = memchr(data, '=', size);
......@@ -983,7 +988,7 @@ int main(int argc, char *argv[]) {
}
r = sd_journal_next(j);
} else if (arg_lines > 0) {
} else if (arg_lines >= 0) {
r = sd_journal_seek_tail(j);
if (r < 0) {
log_error("Failed to seek to tail: %s", strerror(-r));
......@@ -1032,7 +1037,7 @@ int main(int argc, char *argv[]) {
}
for (;;) {
while (arg_lines == 0 || arg_follow || n_shown < arg_lines) {
while (arg_lines < 0 || n_shown < arg_lines || (arg_follow && !first_line)) {
int flags;
if (need_seek) {
......@@ -1092,6 +1097,8 @@ int main(int argc, char *argv[]) {
log_error("Couldn't wait for journal event: %s", strerror(-r));
goto finish;
}
first_line = false;
}
finish:
......
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