This patch adds two very simple psql commands: \quit_if and \quit_unless.
Each takes an optional string parameter and evaluates it for truthiness via
ParseVariableBool().
If a true-ish value is passed to \quit_if, psql will behave as if the user
had input \quit.
\quit_unless will do nothing if the value given was true-ish, and will
\quit in any other circumstances.
Examples below show the behavior:
$ psql postgres
psql (10devel)
Type "help" for help.
# \quit_if
# \quit_unless
$ psql postgres
psql (10devel)
Type "help" for help.
# \quit_if f
# \quit_if 0
# \quit_if false
# \quit_if 2
unrecognized value "2" for "\quit_if"; assuming "on"
$ psql postgres
psql (10devel)
Type "help" for help.
# \quit_unless 2
unrecognized value "2" for "\quit_unless"; assuming "on"
# \quit_unless f
$
The need for this patch has arisen from several scripts I've written
recently that were about 97% psql and 3% bash or similar glue language. In
those scripts, there's often a test that says "there is no work to do here,
and that is not an error". I could engineer an optional SELECT 1/0 to
generate an error, but then I have to make the bash script determine
whether that was an error-error or a no-everything-is-ok-error. I also
don't want to wrap hundreds of lines of SQL inside python docstrings (thus
losing syntax highlighting, etc) just to handle one if/then.
Many thanks to Pavel Stehule for brainstorming this one with me.
diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 2410bee..a9b0732 100644
--- a/doc/src/sgml/ref/psql-ref.sgml
+++ b/doc/src/sgml/ref/psql-ref.sgml
@@ -2616,6 +2616,23 @@ lo_import 152801
</listitem>
</varlistentry>
+ <varlistentry>
+ <term><literal>\quit_if <replaceable
class="parameter">string</replaceable> </literal></term>
+ <listitem>
+ <para>
+ Quits the <application>psql</application> program if the string
evaluates to true.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>\quit_unless <replaceable
class="parameter">string</replaceable> </literal></term>
+ <listitem>
+ <para>
+ Quits the <application>psql</application> program unless the string
evaluates to true.
+ </para>
+ </listitem>
+ </varlistentry>
<varlistentry>
<term><literal>\qecho <replaceable
class="parameter">text</replaceable> [ ... ] </literal></term>
diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index a9a2fdb..7b46fbd 100644
--- a/src/bin/psql/command.c
+++ b/src/bin/psql/command.c
@@ -1251,6 +1251,29 @@ exec_command(const char *cmd,
else if (strcmp(cmd, "q") == 0 || strcmp(cmd, "quit") == 0)
status = PSQL_CMD_TERMINATE;
+ /* \quit_if */
+ else if (strcmp(cmd, "quit_if") == 0)
+ {
+ char *opt = psql_scan_slash_option(scan_state,
+
OT_NORMAL, NULL, false);
+
+ if (opt)
+ if (ParseVariableBool(opt, "\\quit_if"))
+ status = PSQL_CMD_TERMINATE;
+ }
+
+ /* \quit_unless */
+ else if (strcmp(cmd, "quit_unless") == 0)
+ {
+ char *opt = psql_scan_slash_option(scan_state,
+
OT_NORMAL, NULL, false);
+
+ if (!opt)
+ status = PSQL_CMD_TERMINATE;
+ else if (! ParseVariableBool(opt, "\\quit_unless"))
+ status = PSQL_CMD_TERMINATE;
+ }
+
/* reset(clear) the buffer */
else if (strcmp(cmd, "r") == 0 || strcmp(cmd, "reset") == 0)
{
diff --git a/src/bin/psql/help.c b/src/bin/psql/help.c
index a69c4dd..db29650 100644
--- a/src/bin/psql/help.c
+++ b/src/bin/psql/help.c
@@ -177,6 +177,8 @@ slashUsage(unsigned short int pager)
fprintf(output, _(" \\gexec execute query, then
execute each value in its result\n"));
fprintf(output, _(" \\gset [PREFIX] execute query and store
results in psql variables\n"));
fprintf(output, _(" \\q quit psql\n"));
+ fprintf(output, _(" \\quit_if [STRING] quit psql if STRING
evaluates to true\n"));
+ fprintf(output, _(" \\quit_unless [STRING] quit psql if STRING does
not evaluate to true\n"));
fprintf(output, _(" \\crosstabview [COLUMNS] execute query and display
results in crosstab\n"));
fprintf(output, _(" \\watch [SEC] execute query every SEC
seconds\n"));
fprintf(output, "\n");
--
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