blogc: add cli option to read list of source files from stdin

this patch adds `-i` option to command line. it will instruct blogc to
read stdin and parse it as a file where each source file is a line and
empty lines and lines starting with `#` are ignored.

this patch makes it possible to use blogc to build big blogs with lots
of pages, that would hit the operating system max command line length
when calling blogc to build pages.

2 files changed, 43 insertions, 5 deletions

diff --git a/man/blogc.1.ronn b/man/blogc.1.ronn
index a97122b..fc865b8 100644
--- a/man/blogc.1.ronn
+++ b/man/blogc.1.ronn
@@ -3,9 +3,15 @@ blogc(1) -- a blog compiler
 
 ## SYNOPSIS
 
-`blogc` `-d` [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>] <SOURCE><br>
-`blogc` `-d` `-l` [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>] [<SOURCE> ...]<br>
-`blogc` `-d` `-l` `-p` <KEY> [`-D` <KEY>=<VALUE> ...] [<SOURCE> ...]<br>
+`blogc` [`-d`] [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>] <SOURCE><br>
+`blogc` `-l` [`-d`] [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>] [<SOURCE> ...]<br>
+`blogc` `-l` `-p` <KEY> [`-d`] [`-D` <KEY>=<VALUE> ...] [<SOURCE> ...]<br>
+`blogc` `-i` [`-d`] [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>] &lt; <FILE_LIST><br>
+`blogc` `-i` `-l` [`-d`] [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>] &lt; <FILE_LIST><br>
+`blogc` `-i` `-l` `-p` <KEY> [`-d`] [`-D` <KEY>=<VALUE> ...] &lt; <FILE_LIST><br>
+`echo` `-e` "<SOURCE>\n..." | `blogc` `-i` [`-d`] [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>]<br>
+`echo` `-e` "<SOURCE>\n..." | `blogc` `-i` `-l` [`-d`] [`-D` <KEY>=<VALUE> ...] `-t` <TEMPLATE> [`-o` <OUTPUT>]<br>
+`echo` `-e` "<SOURCE>\n..." | `blogc` `-i` `-l` `-p` <KEY> [`-d`] [`-D` <KEY>=<VALUE> ...]<br>
 `blogc` [`-h`|`-v`]
 
 ## DESCRIPTION
@@ -33,6 +39,13 @@ designed to be used with make(1).
   * `-d`:
     Activates debug.
 
+  * `-i`:
+    Reads list of source files from standard input. Content of standard input is
+    parsed as a file where each line is a file path. Empty lines and lines
+    starting with `#` are ignored. If some source files are provided to command
+    line while using this option, they will be parsed **before** the files read
+    from standard input.
+
   * `-l`:
     Activates listing mode, allowing user to provide multiple source files. See
     blogc-source(7) for details.
diff --git a/src/blogc/main.c b/src/blogc/main.c
index 35d9f69..35bcd88 100644
--- a/src/blogc/main.c
+++ b/src/blogc/main.c
@@ -27,6 +27,7 @@
 #include "loader.h"
 #include "renderer.h"
 #include "../common/error.h"
+#include "../common/file.h"
 #include "../common/utf8.h"
 #include "../common/utils.h"
 
@@ -40,7 +41,7 @@ blogc_print_help(void)
 {
     printf(
         "usage:\n"
-        "    blogc [-h] [-v] [-d] [-l] [-D KEY=VALUE ...] [-p KEY] [-t TEMPLATE]\n"
+        "    blogc [-h] [-v] [-d] [-i] [-l] [-D KEY=VALUE ...] [-p KEY] [-t TEMPLATE]\n"
         "          [-o OUTPUT] [SOURCE ...] - A blog compiler.\n"
         "\n"
         "positional arguments:\n"
@@ -50,6 +51,7 @@ blogc_print_help(void)
         "    -h            show this help message and exit\n"
         "    -v            show version and exit\n"
         "    -d            enable debug\n"
+        "    -i            read list of source files from standard input\n"
         "    -l            build listing page, from multiple source files\n"
         "    -D KEY=VALUE  set global configuration parameter\n"
         "    -p KEY        show the value of a global configuration parameter\n"
@@ -63,7 +65,7 @@ static void
 blogc_print_usage(void)
 {
     printf(
-        "usage: blogc [-h] [-v] [-d] [-l] [-D KEY=VALUE ...] [-p KEY] [-t TEMPLATE]\n"
+        "usage: blogc [-h] [-v] [-d] [-i] [-l] [-D KEY=VALUE ...] [-p KEY] [-t TEMPLATE]\n"
         "             [-o OUTPUT] [SOURCE ...]\n");
 }
 
@@ -103,6 +105,22 @@ blogc_mkdir_recursive(const char *filename)
 }
 
 
+static bc_slist_t*
+blogc_read_stdin_to_list(bc_slist_t *l)
+{
+    char buffer[4096];
+    while (NULL != fgets(buffer, 4096, stdin)) {
+        char *tmp = bc_str_strip(buffer);
+        if (tmp[0] == '\0')
+            continue;
+        if (tmp[0] == '#')
+            continue;
+        l = bc_slist_append(l, bc_strdup(tmp));
+    }
+    return l;
+}
+
+
 int
 main(int argc, char **argv)
 {
@@ -111,6 +129,7 @@ main(int argc, char **argv)
     int rv = 0;
 
     bool debug = false;
+    bool input_stdin = false;
     bool listing = false;
     char *template = NULL;
     char *output = NULL;
@@ -135,6 +154,9 @@ main(int argc, char **argv)
                 case 'd':
                     debug = true;
                     break;
+                case 'i':
+                    input_stdin = true;
+                    break;
                 case 'l':
                     listing = true;
                     break;
@@ -204,6 +226,9 @@ main(int argc, char **argv)
             sources = bc_slist_append(sources, bc_strdup(argv[i]));
     }
 
+    if (input_stdin)
+        sources = blogc_read_stdin_to_list(sources);
+
     if (!listing && bc_slist_length(sources) == 0) {
         blogc_print_usage();
         fprintf(stderr, "blogc: error: one source file is required\n");