lslogins: add JSON output format mode

This adds the -J and --json options that enable JSON output mode
for the libsmartcols table. JSON output can be especially useful if
another program wants to consume lslogins's data in an easily parse-
able and language independent format.

Each keys's value will be converted into an appropriate JSON data
type, i.e. integers are numbers, empty values are null and others
are strings.

Signed-off-by: Christian Goeschel Ndjomouo <cgoesc2@wgu.edu>

diff --git a/login-utils/lslogins.c b/login-utils/lslogins.c
index 678f75c4c08d35760a73aee2a8996aa420a0ce87..8c732d600d43a47b215fbd202ee5d4ed917212b3 100644 (file)
--- a/login-utils/lslogins.c
+++ b/login-utils/lslogins.c
@@ -64,6 +64,12 @@
 #include "procfs.h"
 #include "timeutils.h"
 
+/* Types used for JSON and --list-columns */
+enum {
+       COLTYPE_STR     = 0,    /* default */
+       COLTYPE_NUM     = 1,    /* always u64 number */
+};
+
 /*
  * column description
  */
@@ -74,6 +80,7 @@ struct lslogins_coldesc {
 
        double whint;   /* width hint */
        long flag;
+       int type;       /* COLTYPE_* column type*/
 };
 
 static int lslogins_flag;
@@ -98,7 +105,8 @@ enum {
        OUT_NEWLINE,
        OUT_RAW,
        OUT_NUL,
-       OUT_PRETTY
+       OUT_PRETTY,
+       OUT_JSON
 };
 
 enum {
@@ -228,33 +236,33 @@ static const char *const pretty_status[] = {
 
 static const struct lslogins_coldesc coldescs[] =
 {
-       [COL_USER]          = { "USER",         N_("user name"), N_("Username"), 0.1, SCOLS_FL_NOEXTREMES },
-       [COL_UID]           = { "UID",          N_("user ID"), "UID", 1, SCOLS_FL_RIGHT},
-       [COL_PWDEMPTY]      = { "PWD-EMPTY",    N_("password not defined"), N_("Password not required (empty)"), 1, SCOLS_FL_RIGHT },
-       [COL_PWDDENY]       = { "PWD-DENY",     N_("login by password disabled"), N_("Login by password disabled"), 1, SCOLS_FL_RIGHT },
-       [COL_PWDLOCK]       = { "PWD-LOCK",     N_("password defined, but locked"), N_("Password is locked"), 1, SCOLS_FL_RIGHT },
-       [COL_PWDMETHOD]     = { "PWD-METHOD",   N_("password encryption method"), N_("Password encryption method"), 0.1 },
-       [COL_NOLOGIN]       = { "NOLOGIN",      N_("log in disabled by nologin(8) or pam_nologin(8)"), N_("No login"), 1, SCOLS_FL_RIGHT },
-       [COL_GROUP]         = { "GROUP",        N_("primary group name"), N_("Primary group"), 0.1 },
-       [COL_GID]           = { "GID",          N_("primary group ID"), "GID", 1, SCOLS_FL_RIGHT },
-       [COL_SGROUPS]       = { "SUPP-GROUPS",  N_("supplementary group names"), N_("Supplementary groups"), 0.1 },
-       [COL_SGIDS]         = { "SUPP-GIDS",    N_("supplementary group IDs"), N_("Supplementary group IDs"), 0.1 },
-       [COL_HOME]          = { "HOMEDIR",      N_("home directory"), N_("Home directory"), 0.1 },
-       [COL_SHELL]         = { "SHELL",        N_("login shell"), N_("Shell"), 0.1 },
-       [COL_GECOS]         = { "GECOS",        N_("full user name"), N_("Gecos field"), 0.1, SCOLS_FL_TRUNC },
-       [COL_LAST_LOGIN]    = { "LAST-LOGIN",   N_("date of last login"), N_("Last login"), 0.1, SCOLS_FL_RIGHT },
-       [COL_LAST_TTY]      = { "LAST-TTY",     N_("last tty used"), N_("Last terminal"), 0.05 },
-       [COL_LAST_HOSTNAME] = { "LAST-HOSTNAME",N_("hostname during the last session"), N_("Last hostname"),  0.1},
-       [COL_FAILED_LOGIN]  = { "FAILED-LOGIN", N_("date of last failed login"), N_("Failed login"), 0.1 },
-       [COL_FAILED_TTY]    = { "FAILED-TTY",   N_("where did the login fail?"), N_("Failed login terminal"), 0.05 },
-       [COL_HUSH_STATUS]   = { "HUSHED",       N_("user's hush settings"), N_("Hushed"), 1, SCOLS_FL_RIGHT },
-       [COL_PWD_WARN]      = { "PWD-WARN",     N_("days user is warned of password expiration"), N_("Password expiration warn interval"), 0.1, SCOLS_FL_RIGHT },
-       [COL_PWD_EXPIR]     = { "PWD-EXPIR",    N_("password expiration date"), N_("Password expiration"), 0.1, SCOLS_FL_RIGHT },
-       [COL_PWD_CTIME]     = { "PWD-CHANGE",   N_("date of last password change"), N_("Password changed"), 0.1, SCOLS_FL_RIGHT},
-       [COL_PWD_CTIME_MIN] = { "PWD-MIN",      N_("number of days required between changes"), N_("Minimum change time"), 0.1, SCOLS_FL_RIGHT },
-       [COL_PWD_CTIME_MAX] = { "PWD-MAX",      N_("max number of days a password may remain unchanged"), N_("Maximum change time"), 0.1, SCOLS_FL_RIGHT },
-       [COL_SELINUX]       = { "CONTEXT",      N_("the user's security context"), N_("Selinux context"), 0.1 },
-       [COL_NPROCS]        = { "PROC",         N_("number of processes run by the user"), N_("Running processes"), 1, SCOLS_FL_RIGHT },
+       [COL_USER]          = { "USER",         N_("user name"), N_("Username"), 0.1, SCOLS_FL_NOEXTREMES, COLTYPE_STR },
+       [COL_UID]           = { "UID",          N_("user ID"), "UID", 1, SCOLS_FL_RIGHT, COLTYPE_NUM},
+       [COL_PWDEMPTY]      = { "PWD-EMPTY",    N_("password not defined"), N_("Password not required (empty)"), 1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_PWDDENY]       = { "PWD-DENY",     N_("login by password disabled"), N_("Login by password disabled"), 1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_PWDLOCK]       = { "PWD-LOCK",     N_("password defined, but locked"), N_("Password is locked"), 1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_PWDMETHOD]     = { "PWD-METHOD",   N_("password encryption method"), N_("Password encryption method"), 0.1, 0, COLTYPE_NUM },
+       [COL_NOLOGIN]       = { "NOLOGIN",      N_("log in disabled by nologin(8) or pam_nologin(8)"), N_("No login"), 1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_GROUP]         = { "GROUP",        N_("primary group name"), N_("Primary group"), 0.1, 0, COLTYPE_STR },
+       [COL_GID]           = { "GID",          N_("primary group ID"), "GID", 1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_SGROUPS]       = { "SUPP-GROUPS",  N_("supplementary group names"), N_("Supplementary groups"), 0.1, 0, COLTYPE_STR },
+       [COL_SGIDS]         = { "SUPP-GIDS",    N_("supplementary group IDs"), N_("Supplementary group IDs"), 0.1, 0, COLTYPE_NUM },
+       [COL_HOME]          = { "HOMEDIR",      N_("home directory"), N_("Home directory"), 0.1, 0, COLTYPE_STR },
+       [COL_SHELL]         = { "SHELL",        N_("login shell"), N_("Shell"), 0.1, 0, COLTYPE_STR },
+       [COL_GECOS]         = { "GECOS",        N_("full user name"), N_("Gecos field"), 0.1, SCOLS_FL_TRUNC, COLTYPE_STR },
+       [COL_LAST_LOGIN]    = { "LAST-LOGIN",   N_("date of last login"), N_("Last login"), 0.1, SCOLS_FL_RIGHT, COLTYPE_STR },
+       [COL_LAST_TTY]      = { "LAST-TTY",     N_("last tty used"), N_("Last terminal"), 0.05, 0, COLTYPE_STR },
+       [COL_LAST_HOSTNAME] = { "LAST-HOSTNAME",N_("hostname during the last session"), N_("Last hostname"), 0.1, 0, COLTYPE_STR},
+       [COL_FAILED_LOGIN]  = { "FAILED-LOGIN", N_("date of last failed login"), N_("Failed login"), 0.1, 0, COLTYPE_STR },
+       [COL_FAILED_TTY]    = { "FAILED-TTY",   N_("where did the login fail?"), N_("Failed login terminal"), 0.05, 0, COLTYPE_STR },
+       [COL_HUSH_STATUS]   = { "HUSHED",       N_("user's hush settings"), N_("Hushed"), 1, SCOLS_FL_RIGHT, COLTYPE_STR },
+       [COL_PWD_WARN]      = { "PWD-WARN",     N_("days user is warned of password expiration"), N_("Password expiration warn interval"), 0.1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_PWD_EXPIR]     = { "PWD-EXPIR",    N_("password expiration date"), N_("Password expiration"), 0.1, SCOLS_FL_RIGHT, COLTYPE_STR },
+       [COL_PWD_CTIME]     = { "PWD-CHANGE",   N_("date of last password change"), N_("Password changed"), 0.1, SCOLS_FL_RIGHT, COLTYPE_STR },
+       [COL_PWD_CTIME_MIN] = { "PWD-MIN",      N_("number of days required between changes"), N_("Minimum change time"), 0.1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_PWD_CTIME_MAX] = { "PWD-MAX",      N_("max number of days a password may remain unchanged"), N_("Maximum change time"), 0.1, SCOLS_FL_RIGHT, COLTYPE_NUM },
+       [COL_SELINUX]       = { "CONTEXT",      N_("the user's security context"), N_("Selinux context"), 0.1, 0, COLTYPE_STR },
+       [COL_NPROCS]        = { "PROC",         N_("number of processes run by the user"), N_("Running processes"), 1, SCOLS_FL_RIGHT, COLTYPE_NUM },
 };
 
 struct lslogins_control {
@@ -1188,6 +1196,17 @@ static int create_usertree(struct lslogins_control *ctl)
        return 0;
 }
 
+static void set_column_type(const struct lslogins_coldesc *cd, struct libscols_column *cl)
+{
+       if (cd->type == COLTYPE_NUM) {
+               scols_column_set_json_type(cl, SCOLS_JSON_NUMBER);
+               scols_column_set_data_type(cl, SCOLS_DATA_U64);
+               return;
+       }
+       scols_column_set_json_type(cl, SCOLS_JSON_STRING);
+       scols_column_set_data_type(cl, SCOLS_DATA_STRING);
+}
+
 static struct libscols_table *setup_table(struct lslogins_control *ctl)
 {
        struct libscols_table *table = scols_new_table();
@@ -1219,21 +1238,28 @@ static struct libscols_table *setup_table(struct lslogins_control *ctl)
                break;
        case OUT_PRETTY:
                scols_table_enable_noheadings(table, 1);
+               break;
+       case OUT_JSON:
+               scols_table_enable_json(table, 1);
        default:
                break;
        }
 
        while (n < ncolumns) {
                int flags = coldescs[columns[n]].flag;
+               struct libscols_column *col;
 
                if (ctl->notrunc)
                        flags &= ~SCOLS_FL_TRUNC;
 
-               if (!scols_table_new_column(table,
+               col = scols_table_new_column(table,
                                coldescs[columns[n]].name,
                                coldescs[columns[n]].whint,
-                               flags))
+                               flags);
+               if (!col)
                        goto fail;
+
+               set_column_type(&coldescs[columns[n]], col);
                ++n;
        }
 
@@ -1466,8 +1492,11 @@ static int print_user_table(struct lslogins_control *ctl)
                print_journal_tail(ctl->journal_path, ctl->uid, 3, ctl->time_mode);
                fputc('\n', stdout);
 #endif
-       } else
+       } else {
+               if (outmode == OUT_JSON)
+                       scols_table_set_name(tb, "logins");
                scols_print_table(tb);
+       }
        return 0;
 }
 
@@ -1544,6 +1573,7 @@ static void __attribute__((__noreturn__)) usage(void)
        fputs(_("     --output-all         output all columns\n"), out);
        fputs(_(" -p, --pwd                display information related to login by password\n"), out);
        fputs(_(" -r, --raw                display in raw mode\n"), out);
+       fputs(_(" -J, --json               display in JSON format mode\n"), out);
        fputs(_(" -s, --system-accs        display system accounts\n"), out);
        fputs(_("     --time-format=<type> display dates in short, full or iso format\n"), out);
        fputs(_(" -u, --user-accs          display user accounts\n"), out);
@@ -1607,6 +1637,7 @@ int main(int argc, char *argv[])
                { "output-all",     no_argument,        0, OPT_OUTPUT_ALL },
                { "last",           no_argument,        0, 'L', },
                { "raw",            no_argument,        0, 'r' },
+               { "json",           no_argument,        0, 'J' },
                { "system-accs",    no_argument,        0, 's' },
                { "time-format",    required_argument,  0, OPT_TIME_FMT },
                { "user-accs",      no_argument,        0, 'u' },
@@ -1627,10 +1658,10 @@ int main(int argc, char *argv[])
 
        static const ul_excl_t excl[] = {       /* rows and cols in ASCII order */
                { 'G', 'o' },
+               { 'J','c','n','r','z' },
                { 'L', 'o' },
                { 'Z', 'o' },
                { 'a', 'o' },
-               { 'c','n','r','z' },
                { 'o', 'p' },
                { 0 }
        };
@@ -1647,7 +1678,7 @@ int main(int argc, char *argv[])
        add_column(columns, ncolumns++, COL_UID);
        add_column(columns, ncolumns++, COL_USER);
 
-       while ((c = getopt_long(argc, argv, "acefGg:hLl:no:prsuVyzZ",
+       while ((c = getopt_long(argc, argv, "acefGg:hJLl:no:prsuVyzZ",
                                longopts, NULL)) != -1) {
 
                err_exclusive_options(c, longopts, excl, excl_st);
@@ -1705,6 +1736,9 @@ int main(int argc, char *argv[])
                case 'r':
                        outmode = OUT_RAW;
                        break;
+               case 'J':
+                       outmode = OUT_JSON;
+                       break;
                case 's':
                        ctl->SYS_UID_MIN = getlogindefs_num("SYS_UID_MIN", UL_SYS_UID_MIN);
                        ctl->SYS_UID_MAX = getlogindefs_num("SYS_UID_MAX", UL_SYS_UID_MAX);