Add a -i option to sed(1) to do inplace editing, to give us an alternative to

Perl for such things.  The key difference to Perl is that a backup extension
*MUST* be specified, because on one hand it isn't recommended to have options
which optionally take a parameter, and on the other hand, it'd be slightly
unpleasent to implement proper handling for that.

The difference between this and the version posted to developers@ is that it
does handle multiple files in argv after the getopt(3) handling "correctly",
in that the inplace editing-specific code has been moved out to a function,
and that function is used beyond the first file in our linked list.

This option has been documented as FreeBSD-specific in the manpage.

Reviewed by:	developers@ (got feedback from: des, fanf, sobomax, roberto,
		obrien)
MFC after:	1 week

2 files changed, 77 insertions, 3 deletions

diff --git a/usr.bin/sed/main.c b/usr.bin/sed/main.c
index 6e5b4b7..990e9aa 100644
--- a/usr.bin/sed/main.c
+++ b/usr.bin/sed/main.c
@@ -48,7 +48,8 @@ static const char copyright[] =
 static const char sccsid[] = "@(#)main.c	8.2 (Berkeley) 1/3/94";
 #endif
 
-#include <sys/types.h>
+#include <sys/param.h>
+#include <sys/stat.h>
 
 #include <err.h>
 #include <errno.h>
@@ -101,11 +102,13 @@ int rflags = 0;
  * units, but span across input files.
  */
 const char *fname;		/* File name. */
+const char *inplace;		/* Inplace edit file extension. */
 u_long linenum;
 int lastline;			/* TRUE on the last line of the last file */
 
 static void add_compunit(enum e_cut, char *);
 static void add_file(char *);
+static int inplace_edit(char **);
 static void usage(void);
 
 int
@@ -119,7 +122,9 @@ main(argc, argv)
 	(void) setlocale(LC_ALL, "");
 
 	fflag = 0;
-	while ((c = getopt(argc, argv, "Eae:f:n")) != -1)
+	inplace = NULL;
+
+	while ((c = getopt(argc, argv, "Eae:f:i:n")) != -1)
 		switch (c) {
 		case 'E':
 			rflags = REG_EXTENDED;
@@ -139,6 +144,9 @@ main(argc, argv)
 			fflag = 1;
 			add_compunit(CU_FILE, optarg);
 			break;
+		case 'i':
+			inplace = optarg;
+			break;
 		case 'n':
 			nflag = 1;
 			break;
@@ -300,9 +308,15 @@ mf_fgets(sp, spflag)
 				return (0);
 			}
 			if (files->fname == NULL) {
+				if (inplace != NULL)
+					errx(1, "-i may not be used with stdin");
 				f = stdin;
 				fname = "stdin";
 			} else {
+				if (inplace != NULL) {
+					if (inplace_edit(&files->fname) == -1)
+						continue;
+				}
 				fname = files->fname;
 				if ((f = fopen(fname, "r")) == NULL)
 					err(1, "%s", fname);
@@ -340,9 +354,15 @@ mf_fgets(sp, spflag)
 			return (1);
 		}
 		if (files->fname == NULL) {
+			if (inplace != NULL)
+				errx(1, "-i may not be used with stdin");
 			f = stdin;
 			fname = "stdin";
 		} else {
+			if (inplace != NULL) {
+				if (inplace_edit(&files->fname) == -1)
+					continue;
+			}
 			fname = files->fname;
 			if ((f = fopen(fname, "r")) == NULL)
 				err(1, "%s", fname);
@@ -387,3 +407,47 @@ add_file(s)
 	fp->fname = s;
 	fl_nextp = &fp->next;
 }
+
+/*
+ * Modify a pointer to a filename for inplace editing and reopen stdout
+ */
+static int
+inplace_edit(fname)
+	char **fname;
+{
+	struct stat orig;
+	int input, output;
+	char backup[MAXPATHLEN];
+	char *buffer;
+
+	if (lstat(*fname, &orig) == -1)
+		err(1, "lstat");
+	if ((orig.st_mode & S_IFREG) == 0) {
+		warnx("cannot inplace edit %s, not a regular file", fname);
+		return -1;
+	}
+
+	strlcpy(backup, *fname, MAXPATHLEN);
+	strlcat(backup, inplace, MAXPATHLEN);
+
+	input = open(*fname, O_RDONLY);
+	if (input == -1)
+		err(1, "open(%s)", fname);
+	output = open(backup, O_WRONLY|O_CREAT);
+	if (output == -1)
+		err(1, "open(%s)", backup);
+	if (fchmod(output, orig.st_mode & ~S_IFMT) == -1)
+		err(1, "chmod");
+	buffer = malloc(orig.st_size);
+	if (buffer == NULL)
+		errx(1, "malloc failed");
+	if (read(input, buffer, orig.st_size) == -1)
+		err(1, "read");
+	if (write(output, buffer, orig.st_size) == -1)
+		err(1, "write");
+	close(input);
+	close(output);
+	freopen(*fname, "w", stdout);
+	*fname = strdup(backup);
+	return 0;
+}
diff --git a/usr.bin/sed/sed.1 b/usr.bin/sed/sed.1
index f46201a..4005463 100644
--- a/usr.bin/sed/sed.1
+++ b/usr.bin/sed/sed.1
@@ -35,7 +35,7 @@
 .\"	@(#)sed.1	8.2 (Berkeley) 12/30/93
 .\" $FreeBSD$
 .\"
-.Dd December 30, 1993
+.Dd Mar 7, 2002
 .Dt SED 1
 .Os
 .Sh NAME
@@ -50,6 +50,7 @@
 .Op Fl Ean
 .Op Fl e Ar command
 .Op Fl f Ar command_file
+.Op Fl i Ar extension
 .Op Ar
 .Sh DESCRIPTION
 The
@@ -98,6 +99,9 @@ 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
+Edit files in-place, saving backups with the specified
+.Ar extension .
 .It Fl n
 By default, each line of input is echoed to the standard output after
 all of the commands have been applied to it.
@@ -513,3 +517,9 @@ The
 function is expected to be a superset of the
 .St -p1003.2
 specification.
+.Pp
+The
+.Fl i
+option is a non-standard
+.Fx
+extension and may not be available on other operating systems.