Change the semantics of -i (in-place editing) so that it treats

each file independently from other files.  The new semantics are
desired in the most of practical cases, e.g.: delete lines 5-9
from each file.

Keep the previous semantics of -i under a new option, -I, which
uses a single continuous address space covering all files to edit
in-place -- they are too cool to just drop them.

Add regression tests for -i and -I.

Approved by:	dds
Compared with:	GNU sed
Discussed on:	-hackers
MFC after:	2 weeks

1 files changed, 53 insertions, 7 deletions

diff --git a/usr.bin/sed/sed.1 b/usr.bin/sed/sed.1
index f6a86d5..5e28f04 100644
--- a/usr.bin/sed/sed.1
+++ b/usr.bin/sed/sed.1
@@ -46,6 +46,7 @@
 .Op Fl Ealn
 .Op Fl e Ar command
 .Op Fl f Ar command_file
+.Op Fl I Ar extension
 .Op Fl i Ar extension
 .Op Ar
 .Sh DESCRIPTION
@@ -95,7 +96,7 @@ Append the editing commands found in the file
 .Ar command_file
 to the list of commands.
 The editing commands should each be listed on a separate line.
-.It Fl i Ar extension
+.It Fl I Ar extension
 Edit files in-place, saving backups with the specified
 .Ar extension .
 If a zero-length
@@ -105,6 +106,36 @@ It is not recommended to give a zero-length
 .Ar extension
 when in-place editing files, as you risk corruption or partial content
 in situations where disk space is exhausted, etc.
+.Pp
+Note that in-place editing with
+.Fl I
+still takes place in a single continuous line address space covering
+all files, although each file preserves its individuality instead of
+forming one output stream.
+The line counter is never reset between files, address ranges can span
+file boundaries, and the
+.Dq $
+address matches only the last line of the last file.
+(See
+.Sx "Sed Addresses" . )
+That can lead to unexpected results in many cases of in-place editing,
+where using
+.Fl i
+is desired.
+.It Fl i Ar extension
+Edit files in-place similarly to
+.Fl I ,
+but treat each file independently from other files.
+In particular, line numbers in each file start at 1,
+the
+.Dq $
+address matches the last line of the current file,
+and address ranges are limited to the current file.
+(See
+.Sx "Sed Addresses" . )
+The net result is as though each file were edited by a separate
+.Nm
+instance.
 .It Fl l
 Make output line buffered.
 .It Fl n
@@ -140,13 +171,28 @@ Some of the functions use a
 .Em "hold space"
 to save all or part of the pattern space for subsequent retrieval.
 .Sh "Sed Addresses"
-An address is not required, but if specified must be a number (that counts
+An address is not required, but if specified must have one of the
+following formats:
+.Bl -bullet -offset indent
+.It
+a number that counts
 input lines
-cumulatively across input files), a dollar
+cumulatively across input files (or in each file independently
+if a
+.Fl i
+option is in effect);
+.It
+a dollar
 .Pq Dq $
-character that addresses the last line of input, or a context address
-(which consists of a regular expression preceded and followed by a
-delimiter).
+character that addresses the last line of input (or the last line
+of the current file if a
+.Fl i
+option was specified);
+.It
+a context address
+that consists of a regular expression preceded and followed by a
+delimiter.
+.El
 .Pp
 A command line with no addresses selects every pattern space.
 .Pp
@@ -533,7 +579,7 @@ utility is expected to be a superset of the
 specification.
 .Pp
 The
-.Fl E , a
+.Fl E , I , a
 and
 .Fl i
 options are non-standard