shell: Fix "read -d ''" behavior

With bash's read builtin it is possible to read from a file (e.g.
device-tree) until the first '\0' character:

IFS= read -r -d '' VARIABLE < file

In busybox ash the -d extension is also implemented, but checking the
read character for '\0' has to be performed after comparing with the
delimiter.

Signed-off-by: Christian Eggers <ceggers@arri.de>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

5 files changed, 6 insertions, 2 deletions

diff --git a/shell/ash_test/ash-read/read_d0.right b/shell/ash_test/ash-read/read_d0.right
new file mode 100644
index 000000000..9daeafb98
--- /dev/null
+++ b/shell/ash_test/ash-read/read_d0.right
@@ -0,0 +1 @@
+test
diff --git a/shell/ash_test/ash-read/read_d0.tests b/shell/ash_test/ash-read/read_d0.tests
new file mode 100755
index 000000000..630d80787
--- /dev/null
+++ b/shell/ash_test/ash-read/read_d0.tests
@@ -0,0 +1 @@
+printf 'test\0zest\n' | (read -d '' reply; echo "$reply")
diff --git a/shell/hush_test/hush-read/read_d0.right b/shell/hush_test/hush-read/read_d0.right
new file mode 100644
index 000000000..9daeafb98
--- /dev/null
+++ b/shell/hush_test/hush-read/read_d0.right
@@ -0,0 +1 @@
+test
diff --git a/shell/hush_test/hush-read/read_d0.tests b/shell/hush_test/hush-read/read_d0.tests
new file mode 100755
index 000000000..630d80787
--- /dev/null
+++ b/shell/hush_test/hush-read/read_d0.tests
@@ -0,0 +1 @@
+printf 'test\0zest\n' | (read -d '' reply; echo "$reply")
diff --git a/shell/shell_common.c b/shell/shell_common.c
index 12c4a073c..42c4c9c97 100644
--- a/shell/shell_common.c
+++ b/shell/shell_common.c
@@ -209,8 +209,6 @@ shell_builtin_read(struct builtin_read_params *params)
                 }
 
                 c = buffer[bufpos];
-                if (c == '\0')
-                        continue;
                 if (!(read_flags & BUILTIN_READ_RAW)) {
                         if (backslash) {
                                 backslash = 0;
@@ -225,6 +223,8 @@ shell_builtin_read(struct builtin_read_params *params)
                 }
                 if (c == delim) /* '\n' or -d CHAR */
                         break;
+                if (c == '\0')
+                        continue;
 
                 /* $IFS splitting. NOT done if we run "read"
                  * without variable names (bash compat).