awk: fix FS assignment behavior. Closes 5108

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

2 files changed, 19 insertions, 0 deletions

diff --git a/editors/awk.c b/editors/awk.c
index d69720d64..42f6ef866 100644
--- a/editors/awk.c
+++ b/editors/awk.c
@@ -1812,6 +1812,18 @@ static void handle_special(var *v)
                 is_f0_split = FALSE;
 
         } else if (v == intvar[FS]) {
+                /*
+                 * The POSIX-2008 standard says that changing FS should have no effect on the
+                 * current input line, but only on the next one. The language is:
+                 *
+                 * > Before the first reference to a field in the record is evaluated, the record
+                 * > shall be split into fields, according to the rules in Regular Expressions,
+                 * > using the value of FS that was current at the time the record was read.
+                 *
+                 * So, split up current line before assignment to FS:
+                 */
+                split_f0();
+
                 mk_splitter(getvar_s(v), &fsplitter);
 
         } else if (v == intvar[RS]) {
diff --git a/testsuite/awk.tests b/testsuite/awk.tests
index d4c390d31..f9c3b6b4d 100755
--- a/testsuite/awk.tests
+++ b/testsuite/awk.tests
@@ -217,4 +217,11 @@ end d
 testing "awk handles empty ()" \
         "awk 'BEGIN {print()}' 2>&1" "awk: cmd. line:1: Empty sequence\n" "" ""
 
+testing "awk FS assignment" "awk '{FS=\":\"; print \$1}'" \
+        "a:b\ne\n" \
+        "" \
+        "a:b c:d\ne:f g:h"
+
+# testing "description" "command" "result" "infile" "stdin"
+
 exit $FAILCOUNT