cat,nl: fix handling of open errors

$ cat -n does_not_exist; echo $?
cat: does_not_exist: No such file or directory
1

function                                             old     new   delta
print_numbered_lines                                 118     129     +11
nl_main                                              196     201      +5
cat_main                                             421     425      +4
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 3/0 up/down: 20/0)               Total: 20 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 8 insertions, 2 deletions

diff --git a/libbb/print_numbered_lines.c b/libbb/print_numbered_lines.c
index 9a8a51440..d6459d7c3 100644
--- a/libbb/print_numbered_lines.c
+++ b/libbb/print_numbered_lines.c
@@ -8,12 +8,16 @@
 
 #include "libbb.h"
 
-void FAST_FUNC print_numbered_lines(struct number_state *ns, const char *filename)
+int FAST_FUNC print_numbered_lines(struct number_state *ns, const char *filename)
 {
         FILE *fp = fopen_or_warn_stdin(filename);
-        unsigned N = ns->start;
+        unsigned N;
         char *line;
 
+        if (!fp)
+                return EXIT_FAILURE;
+
+        N = ns->start;
         while ((line = xmalloc_fgetline(fp)) != NULL) {
                 if (ns->all
                  || (ns->nonempty && line[0])
@@ -27,4 +31,6 @@ void FAST_FUNC print_numbered_lines(struct number_state *ns, const char *filenam
         ns->start = N;
 
         fclose(fp);
+
+        return EXIT_SUCCESS;
 }