Small size optimization from Aaron Lehmann
[oweals/busybox.git] / sed.c
diff --git a/sed.c b/sed.c
index 115783f0916973e342439094695d73c2af9ebeb0..a18cfc7c306e0d444c61ddbc5714c444469a9ee7 100644 (file)
--- a/sed.c
+++ b/sed.c
@@ -1,8 +1,8 @@
 /*
  * sed.c - very minimalist version of sed
  *
- * Copyright (C) 1999,2000 by Lineo, inc.
- * Written by Mark Whitley <markw@lineo.com>, <markw@enol.com>
+ * Copyright (C) 1999,2000,2001 by Lineo, inc.
+ * Written by Mark Whitley <markw@lineo.com>, <markw@codepoet.org>
  *
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -27,6 +27,8 @@
         - address matching: num|/matchstr/[,num|/matchstr/|$]command
         - commands: (p)rint, (d)elete, (s)ubstitue (with g & I flags)
         - edit commands: (a)ppend, (i)nsert, (c)hange
+        - file commands: (r)ead
+        - backreferences in substitution expressions (\1, \2...\9)
         
         (Note: Specifying an address (range) to match is *optional*; commands
         default to the whole pattern space if no specific address match was
        Unsupported features:
 
         - transliteration (y/source-chars/dest-chars/) (use 'tr')
-        - no support for characters other than the '/' character for regex matches
         - no pattern space hold space storing / swapping (x, etc.)
         - no labels / branching (: label, b, t, and friends)
         - and lots, lots more.
-
 */
 
 #include <stdio.h>
-#include <stdlib.h> /* for realloc() */
 #include <unistd.h> /* for getopt() */
 #include <regex.h>
 #include <string.h> /* for strdup() */
 #include <errno.h>
 #include <ctype.h> /* for isspace() */
-#include "internal.h"
-
+#include <stdlib.h>
+#include "busybox.h"
 
 /* externs */
+extern void xregcomp(regex_t *preg, const char *regex, int cflags);
 extern int optind; /* in unistd.h */
 extern char *optarg; /* ditto */
 
 /* options */
 static int be_quiet = 0;
 
+
 struct sed_cmd {
 
+
+       /* GENERAL FIELDS */
+       char delimiter;     /* The delimiter used to separate regexps */
+
        /* address storage */
        int beg_line; /* 'sed 1p'   0 == no begining line, apply commands to all lines */
        int end_line; /* 'sed 1,3p' 0 == no end line, use only beginning. -1 == $ */
@@ -70,13 +75,27 @@ struct sed_cmd {
        /* the command */
        char cmd; /* p,d,s (add more at your leisure :-) */
 
-       /* substitution command specific fields */
-       regex_t *sub_match; /* sed -e 's/sub_match/replace/' */
-       char *replace; /* sed -e 's/sub_match/replace/' XXX: who will hold the \1 \2 \3s? */
+
+       /* SUBSTITUTION COMMAND SPECIFIC FIELDS */
+
+       /* sed -e 's/sub_match/replace/' */
+       regex_t *sub_match;
+       char *replace;
+       unsigned int num_backrefs:4; /* how many back references (\1..\9) */
+                       /* Note:  GNU/POSIX sed does not save more than nine backrefs, so
+                        * we only use 4 bits to hold the number */
        unsigned int sub_g:1; /* sed -e 's/foo/bar/g' (global) */
+       unsigned int sub_p:2; /* sed -e 's/foo/bar/p' (print substitution) */
+
+
+       /* EDIT COMMAND (a,i,c) SPEICIFIC FIELDS */
 
-       /* edit command (a,i,c) speicific field */
        char *editline;
+
+
+       /* FILE COMMAND (r) SPEICIFIC FIELDS */
+
+       char *filename;
 };
 
 /* globals */
@@ -85,23 +104,7 @@ static int ncmds = 0; /* number of sed commands */
 
 /*static char *cur_file = NULL;*/ /* file currently being processed XXX: do I need this? */
 
-static const char sed_usage[] =
-       "sed [-Vhnef] pattern [files...]\n"
-#ifndef BB_FEATURE_TRIVIAL_HELP
-       "\n"
-       "-n\tsuppress automatic printing of pattern space\n"
-       "-e script\tadd the script to the commands to be executed\n"
-       "-f scriptfile\tadd the contents of script-file to the commands to be executed\n"
-       "-h\tdisplay this help message\n"
-       "-V\toutput version information and exit\n"
-       "\n"
-       "If no -e or -f is given, the first non-option argument is taken as the\n"
-       "sed script to interpret. All remaining arguments are names of input\n"
-       "files; if no input files are specified, then the standard input is read.\n"
-#endif
-       ;
-
-#if 0
+#ifdef BB_FEATURE_CLEAN_UP
 static void destroy_cmd_strs()
 {
        if (sed_cmds == NULL)
@@ -132,155 +135,149 @@ static void destroy_cmd_strs()
 }
 #endif
 
-/*
- * trim_str - trims leading and trailing space from a string
- * 
- * Note: This returns a malloc'ed string so you must store and free it
- * XXX: This should be in the utility.c file.
- */
-static char *trim_str(const char *str)
-{
-       int i;
-       char *retstr = strdup(str);
-
-       /* trim leading whitespace */
-       memmove(retstr, &retstr[strspn(retstr, " \n\t\v")], strlen(retstr));
-
-       /* trim trailing whitespace */
-       i = strlen(retstr) - 1;
-       while (isspace(retstr[i]))
-               i--;
-       retstr[++i] = 0;
-
-       /* Aside: 
-        *
-        * you know, a strrspn() would really be nice cuz then we could say:
-        * 
-        * retstr[strlen(retstr) - strrspn(retstr, " \n\t\v") + 1] = 0;
-        */
-       
-       return retstr;
-}
 
 /*
- * index_of_unescaped_slash - walks left to right through a string beginning
- * at a specified index and returns the index of the next unescaped slash.
+ * index_of_next_unescaped_regexp_delim - walks left to right through a string
+ * beginning at a specified index and returns the index of the next regular
+ * expression delimiter (typically a forward * slash ('/')) not preceeded by 
+ * a backslash ('\').
  */
-static int index_of_next_unescaped_slash(const char *str, int idx)
+static int index_of_next_unescaped_regexp_delim(struct sed_cmd *sed_cmd, const char *str, int idx)
 {
-       do {
-               idx++;
-               /* test if we've hit the end */
-               if (str[idx] == 0)
-                       return -1;
-       } while (str[idx] != '/' && str[idx - 1] != '\\');
+       for ( ; str[idx]; idx++) {
+               if (str[idx] == sed_cmd->delimiter && str[idx-1] != '\\')
+                       return idx;
+       }
 
-       return idx;
+       /* if we make it to here, we've hit the end of the string */
+       return -1;
 }
 
 /*
  * returns the index in the string just past where the address ends.
  */
-static int get_address(const char *str, int *line, regex_t **regex)
+static int get_address(struct sed_cmd *sed_cmd, const char *str, int *linenum, regex_t **regex)
 {
        char *my_str = strdup(str);
        int idx = 0;
+       char olddelimiter;
+       olddelimiter = sed_cmd->delimiter;
+       sed_cmd->delimiter = '/';
 
        if (isdigit(my_str[idx])) {
                do {
                        idx++;
                } while (isdigit(my_str[idx]));
                my_str[idx] = 0;
-               *line = atoi(my_str);
+               *linenum = atoi(my_str);
        }
        else if (my_str[idx] == '$') {
-               *line = -1;
+               *linenum = -1;
                idx++;
        }
        else if (my_str[idx] == '/') {
-               idx = index_of_next_unescaped_slash(my_str, idx);
+               idx = index_of_next_unescaped_regexp_delim(sed_cmd, my_str, ++idx);
                if (idx == -1)
-                       fatalError("unterminated match expression\n");
+                       error_msg_and_die("unterminated match expression");
                my_str[idx] = '\0';
                *regex = (regex_t *)xmalloc(sizeof(regex_t));
                xregcomp(*regex, my_str+1, REG_NEWLINE);
                idx++; /* so it points to the next character after the last '/' */
        }
        else {
-               fprintf(stderr, "sed.c:get_address: no address found in string\n");
-               fprintf(stderr, "\t(you probably didn't check the string you passed me)\n");
+               error_msg("get_address: no address found in string\n"
+                               "\t(you probably didn't check the string you passed me)");
                idx = -1;
        }
 
        free(my_str);
+       sed_cmd->delimiter = olddelimiter;
        return idx;
 }
 
-static char *strdup_substr(const char *str, int start, int end)
-{
-       int size = end - start + 1;
-       char *newstr = xmalloc(size);
-       memcpy(newstr, str+start, size-1);
-       newstr[size-1] = '\0';
-       return newstr;
-}
-
-static void parse_subst_cmd(struct sed_cmd *sed_cmd, const char *substr)
+static int parse_subst_cmd(struct sed_cmd *sed_cmd, const char *substr)
 {
        int oldidx, cflags = REG_NEWLINE;
        char *match;
        int idx = 0;
+       int j;
 
        /*
         * the string that gets passed to this function should look like this:
-        *    s/match/replace/gI
-        *    ||     |        ||
+        *    s/match/replace/gIp
+        *    ||     |        |||
         *    mandatory       optional
         *
         *    (all three of the '/' slashes are mandatory)
         */
 
-       /* verify that the 's' is followed by a 'slash' */
-       if (substr[++idx] != '/')
-               fatalError("bad format in substitution expression\n");
+       /* verify that the 's' is followed by something.  That something
+        * (typically a 'slash') is now our regexp delimiter... */
+       if (!substr[++idx])
+               error_msg_and_die("bad format in substitution expression");
+       else
+           sed_cmd->delimiter=substr[idx];
 
        /* save the match string */
        oldidx = idx+1;
-       idx = index_of_next_unescaped_slash(substr, idx);
+       idx = index_of_next_unescaped_regexp_delim(sed_cmd, substr, ++idx);
        if (idx == -1)
-               fatalError("bad format in substitution expression\n");
-       match = strdup_substr(substr, oldidx, idx);
+               error_msg_and_die("bad format in substitution expression");
+       match = xstrndup(substr + oldidx, idx - oldidx);
+
+       /* determine the number of back references in the match string */
+       /* Note: we compute this here rather than in the do_subst_command()
+        * function to save processor time, at the expense of a little more memory
+        * (4 bits) per sed_cmd */
+       
+       /* sed_cmd->num_backrefs = 0; */ /* XXX: not needed? --apparently not */ 
+       for (j = 0; match[j]; j++) {
+               /* GNU/POSIX sed does not save more than nine backrefs */
+               if (match[j] == '\\' && match[j+1] == '(' && sed_cmd->num_backrefs <= 9)
+                       sed_cmd->num_backrefs++;
+       }
 
        /* save the replacement string */
        oldidx = idx+1;
-       idx = index_of_next_unescaped_slash(substr, idx);
+       idx = index_of_next_unescaped_regexp_delim(sed_cmd, substr, ++idx);
        if (idx == -1)
-               fatalError("bad format in substitution expression\n");
-       sed_cmd->replace = strdup_substr(substr, oldidx, idx);
+               error_msg_and_die("bad format in substitution expression");
+       sed_cmd->replace = xstrndup(substr + oldidx, idx - oldidx);
 
        /* process the flags */
        while (substr[++idx]) {
                switch (substr[idx]) {
-               case 'g':
-                       sed_cmd->sub_g = 1;
-                       break;
-               case 'I':
-                       cflags |= REG_ICASE;
-                       break;
-               default:
-                       fatalError("bad option in substitution expression\n");
+                       case 'g':
+                               sed_cmd->sub_g = 1;
+                               break;
+                       case 'I':
+                               cflags |= REG_ICASE;
+                               break;
+                       case 'p':
+                               sed_cmd->sub_p = 1;
+                               break;
+                       default:
+                               /* any whitespace or semicolon trailing after a s/// is ok */
+                               if (strchr("; \t\v\n\r", substr[idx]))
+                                       goto out;
+                               /* else */
+                               error_msg_and_die("bad option in substitution expression");
                }
        }
-               
-       /* compile the regex */
+
+out:   
+       /* compile the match string into a regex */
        sed_cmd->sub_match = (regex_t *)xmalloc(sizeof(regex_t));
        xregcomp(sed_cmd->sub_match, match, cflags);
        free(match);
+
+       return idx;
 }
 
-static void parse_edit_cmd(struct sed_cmd *sed_cmd, const char *editstr)
+static int parse_edit_cmd(struct sed_cmd *sed_cmd, const char *editstr)
 {
        int idx = 0;
+       int slashes_eaten = 0;
        char *ptr; /* shorthand */
 
        /*
@@ -306,32 +303,90 @@ static void parse_edit_cmd(struct sed_cmd *sed_cmd, const char *editstr)
         */
 
        if (editstr[1] != '\\' && (editstr[2] != '\n' || editstr[2] != '\r'))
-               fatalError("bad format in edit expression\n");
+               error_msg_and_die("bad format in edit expression");
 
        /* store the edit line text */
-       sed_cmd->editline = strdup(&editstr[3]);
+       /* make editline big enough to accomodate the extra '\n' we will tack on
+        * to the end */
+       sed_cmd->editline = xmalloc(strlen(&editstr[3]) + 2);
+       strcpy(sed_cmd->editline, &editstr[3]);
        ptr = sed_cmd->editline;
 
        /* now we need to go through * and: s/\\[\r\n]$/\n/g on the edit line */
        while (ptr[idx]) {
-               while (ptr[idx] != '\\' && (ptr[idx+1] != '\n' || ptr[idx+1] != '\r')) {
+               while (ptr[idx] != '\\' || (ptr[idx+1] != '\n' && ptr[idx+1] != '\r')) {
                        idx++;
                        if (!ptr[idx]) {
-                               ptr[idx] = '\n';
-                               ptr[idx+1] = 0;
-                               return;
+                               goto out;
                        }
                }
                /* move the newline over the '\' before it (effectively eats the '\') */
                memmove(&ptr[idx], &ptr[idx+1], strlen(&ptr[idx+1]));
                ptr[strlen(ptr)-1] = 0;
+               slashes_eaten++;
                /* substitue \r for \n if needed */
                if (ptr[idx] == '\r')
                        ptr[idx] = '\n';
        }
+
+out:
+       /* this accounts for discrepancies between the modified string and the
+        * original string passed in to this function */
+       idx += slashes_eaten;
+
+       /* figure out if we need to add a newline */
+       if (ptr[idx-1] != '\n') {
+               ptr[idx] = '\n';
+               idx++;
+       }
+
+       /* terminate string */
+       ptr[idx]= 0;
+       /* adjust for opening 2 chars [aic]\ */
+       idx += 2;
+
+       return idx;
 }
 
-static void parse_cmd_str(struct sed_cmd *sed_cmd, const char *cmdstr)
+
+static int parse_file_cmd(struct sed_cmd *sed_cmd, const char *filecmdstr)
+{
+       int idx = 0;
+       int filenamelen = 0;
+
+       /*
+        * the string that gets passed to this function should look like this:
+        *    '[ ]filename'
+        *      |  |
+        *      |  a filename
+        *      |
+        *     optional whitespace
+
+        *   re: the file to be read, the GNU manual says the following: "Note that
+        *   if filename cannot be read, it is treated as if it were an empty file,
+        *   without any error indication." Thus, all of the following commands are
+        *   perfectly leagal:
+        *
+        *   sed -e '1r noexist'
+        *   sed -e '1r ;'
+        *   sed -e '1r'
+        */
+
+       /* the file command may be followed by whitespace; move past it. */
+       while (isspace(filecmdstr[++idx]))
+               { ; }
+               
+       /* the first non-whitespace we get is a filename. the filename ends when we
+        * hit a normal sed command terminator or end of string */
+       filenamelen = strcspn(&filecmdstr[idx], "; \n\r\t\v\0");
+       sed_cmd->filename = xmalloc(filenamelen + 1);
+       safe_strncpy(sed_cmd->filename, &filecmdstr[idx], filenamelen + 1);
+
+       return idx + filenamelen;
+}
+
+
+static char *parse_cmd_str(struct sed_cmd *sed_cmd, const char *cmdstr)
 {
        int idx = 0;
 
@@ -343,47 +398,71 @@ static void parse_cmd_str(struct sed_cmd *sed_cmd, const char *cmdstr)
 
        /* first part (if present) is an address: either a number or a /regex/ */
        if (isdigit(cmdstr[idx]) || cmdstr[idx] == '/')
-               idx = get_address(cmdstr, &sed_cmd->beg_line, &sed_cmd->beg_match);
+               idx = get_address(sed_cmd, cmdstr, &sed_cmd->beg_line, &sed_cmd->beg_match);
 
        /* second part (if present) will begin with a comma */
        if (cmdstr[idx] == ',')
-               idx += get_address(&cmdstr[++idx], &sed_cmd->end_line, &sed_cmd->end_match);
+               idx += get_address(sed_cmd, &cmdstr[++idx], &sed_cmd->end_line, &sed_cmd->end_match);
 
        /* last part (mandatory) will be a command */
        if (cmdstr[idx] == '\0')
-               fatalError("missing command\n");
-       if (!strchr("pdsaic", cmdstr[idx])) /* <-- XXX add new commands here */
-               fatalError("invalid command\n");
+               error_msg_and_die("missing command");
        sed_cmd->cmd = cmdstr[idx];
 
-       /* special-case handling for (s)ubstitution */
-       if (sed_cmd->cmd == 's')
-               parse_subst_cmd(sed_cmd, &cmdstr[idx]);
-       
-       /* special-case handling for (a)ppend, (i)nsert, and (c)hange */
-       if (strchr("aic", cmdstr[idx])) {
+       /* if it was a single-letter command that takes no arguments (such as 'p'
+        * or 'd') all we need to do is increment the index past that command */
+       if (strchr("pd", cmdstr[idx])) {
+               idx++;
+       }
+       /* handle (s)ubstitution command */
+       else if (sed_cmd->cmd == 's') {
+               idx += parse_subst_cmd(sed_cmd, &cmdstr[idx]);
+       }
+       /* handle edit cmds: (a)ppend, (i)nsert, and (c)hange */
+       else if (strchr("aic", sed_cmd->cmd)) {
+               if ((sed_cmd->end_line || sed_cmd->end_match) && sed_cmd->cmd != 'c')
+                       error_msg_and_die("only a beginning address can be specified for edit commands");
+               idx += parse_edit_cmd(sed_cmd, &cmdstr[idx]);
+       }
+       /* handle file cmds: (r)ead */
+       else if (sed_cmd->cmd == 'r') {
                if (sed_cmd->end_line || sed_cmd->end_match)
-                       fatalError("only a beginning address can be specified for edit commands\n");
-               parse_edit_cmd(sed_cmd, &cmdstr[idx]);
+                       error_msg_and_die("Command only uses one address");
+               idx += parse_file_cmd(sed_cmd, &cmdstr[idx]);
        }
+       else {
+               error_msg_and_die("invalid command");
+       }
+
+       /* give back whatever's left over */
+       return (char *)&cmdstr[idx];
 }
 
 static void add_cmd_str(const char *cmdstr)
 {
-       char *my_cmdstr = trim_str(cmdstr);
+       char *mystr = (char *)cmdstr;
 
-       /* if this is a comment, don't even bother */
-       if (my_cmdstr[0] == '#') {
-               free(my_cmdstr);
-               return;
-       }
+       do {
 
-       /* grow the array */
-       sed_cmds = realloc(sed_cmds, sizeof(struct sed_cmd) * (++ncmds));
-       /* zero new element */
-       memset(&sed_cmds[ncmds-1], 0, sizeof(struct sed_cmd));
-       /* load command string into new array element */
-       parse_cmd_str(&sed_cmds[ncmds-1], my_cmdstr);
+               /* trim leading whitespace and semicolons */
+               memmove(mystr, &mystr[strspn(mystr, "; \n\r\t\v")], strlen(mystr));
+               /* if we ate the whole thing, that means there was just trailing
+                * whitespace or a final / no-op semicolon. either way, get out */
+               if (strlen(mystr) == 0)
+                       return;
+               /* if this is a comment, jump past it and keep going */
+               if (mystr[0] == '#') {
+                       mystr = strpbrk(mystr, ";\n\r");
+                       continue;
+               }
+               /* grow the array */
+               sed_cmds = xrealloc(sed_cmds, sizeof(struct sed_cmd) * (++ncmds));
+               /* zero new element */
+               memset(&sed_cmds[ncmds-1], 0, sizeof(struct sed_cmd));
+               /* load command string into new array element, get remainder */
+               mystr = parse_cmd_str(&sed_cmds[ncmds-1], mystr);
+
+       } while (mystr && strlen(mystr));
 }
 
 
@@ -393,155 +472,266 @@ static void load_cmd_file(char *filename)
        char *line;
        char *nextline;
 
-       cmdfile = fopen(filename, "r");
-       if (cmdfile == NULL)
-               fatalError(strerror(errno));
+       cmdfile = xfopen(filename, "r");
 
        while ((line = get_line_from_file(cmdfile)) != NULL) {
                /* if a line ends with '\' it needs the next line appended to it */
                while (line[strlen(line)-2] == '\\' &&
                                (nextline = get_line_from_file(cmdfile)) != NULL) {
-                       line = realloc(line, strlen(line) + strlen(nextline) + 1);
+                       line = xrealloc(line, strlen(line) + strlen(nextline) + 1);
                        strcat(line, nextline);
+                       free(nextline);
                }
+               /* eat trailing newline (if any) --if I don't do this, edit commands
+                * (aic) will print an extra newline */
+               chomp(line);
                add_cmd_str(line);
                free(line);
        }
 }
 
-static int do_subst_command(const struct sed_cmd *sed_cmd, const char *line)
+static void print_subst_w_backrefs(const char *line, const char *replace, regmatch_t *regmatch)
 {
-       int altered = 0;
+       int i;
 
-       /* we only substitute if the substitution 'search' expression matches */
-       if (regexec(sed_cmd->sub_match, line, 0, NULL, 0) == 0) {
-               regmatch_t regmatch;
-               int i;
-               char *ptr = (char *)line;
-
-               while (*ptr) {
-                       /* if we can match the search string... */
-                       if (regexec(sed_cmd->sub_match, ptr, 1, &regmatch, 0) == 0) {
-                               /* print everything before the match, */
-                               for (i = 0; i < regmatch.rm_so; i++)
-                                       fputc(ptr[i], stdout);
-                               /* then print the substitution in its place */
-                               fputs(sed_cmd->replace, stdout);
-                               /* then advance past the match */
-                               ptr += regmatch.rm_eo;
-                               /* and flag that something has changed */
-                               altered++;
-
-                               /* if we're not doing this globally... */
-                               if (!sed_cmd->sub_g)
-                                       break;
-                       }
-                       /* if we COULD NOT match the search string (meaning we've gone past
-                        * all previous instances), get out */
-                       else
-                               break;
+       /* go through the replacement string */
+       for (i = 0; replace[i]; i++) {
+               /* if we find a backreference (\1, \2, etc.) print the backref'ed * text */
+               if (replace[i] == '\\' && isdigit(replace[i+1])) {
+                       int j;
+                       char tmpstr[2];
+                       int backref;
+                       ++i; /* i now indexes the backref number, instead of the leading slash */
+                       tmpstr[0] = replace[i];
+                       tmpstr[1] = 0;
+                       backref = atoi(tmpstr);
+                       /* print out the text held in regmatch[backref] */
+                       for (j = regmatch[backref].rm_so; j < regmatch[backref].rm_eo; j++)
+                               fputc(line[j], stdout);
                }
 
-               /* is there anything left to print? */
-               if (*ptr) 
-                       fputs(ptr, stdout);
-       }
+               /* if we find a backslash escaped character, print the character */
+               else if (replace[i] == '\\') {
+                       ++i;
+                       fputc(replace[i], stdout);
+               }
 
-       return altered;
+               /* if we find an unescaped '&' print out the whole matched text.
+                * fortunately, regmatch[0] contains the indicies to the whole matched
+                * expression (kinda seems like it was designed for just such a
+                * purpose...) */
+               else if (replace[i] == '&' && replace[i-1] != '\\') {
+                       int j;
+                       for (j = regmatch[0].rm_so; j < regmatch[0].rm_eo; j++)
+                               fputc(line[j], stdout);
+               }
+               /* nothing special, just print this char of the replacement string to stdout */
+               else
+                       fputc(replace[i], stdout);
+       }
 }
 
-static int do_sed_command(const struct sed_cmd *sed_cmd, const char *line) 
+static int do_subst_command(const struct sed_cmd *sed_cmd, const char *line)
 {
+       char *hackline = (char *)line;
        int altered = 0;
+       regmatch_t *regmatch = NULL;
 
-       switch (sed_cmd->cmd) {
+       /* we only proceed if the substitution 'search' expression matches */
+       if (regexec(sed_cmd->sub_match, line, 0, NULL, 0) == REG_NOMATCH)
+               return 0;
 
-               case 'p':
-                       fputs(line, stdout);
-                       break;
+       /* whaddaya know, it matched. get the number of back references */
+       regmatch = xmalloc(sizeof(regmatch_t) * (sed_cmd->num_backrefs+1));
 
-               case 'd':
-                       altered++;
-                       break;
+       /* and now, as long as we've got a line to try matching and if we can match
+        * the search string, we make substitutions */
+       while (*hackline && (regexec(sed_cmd->sub_match, hackline,
+                                       sed_cmd->num_backrefs+1, regmatch, 0) == 0) ) {
+               int i;
 
-               case 's':
-                       altered = do_subst_command(sed_cmd, line);
-                       break;
+               /* print everything before the match */
+               for (i = 0; i < regmatch[0].rm_so; i++)
+                       fputc(hackline[i], stdout);
 
-               case 'a':
-                       fputs(line, stdout);
-                       fputs(sed_cmd->editline, stdout);
-                       altered++;
-                       break;
+               /* then print the substitution string */
+               print_subst_w_backrefs(hackline, sed_cmd->replace, regmatch);
 
-               case 'i':
-                       fputs(sed_cmd->editline, stdout);
-                       break;
+               /* advance past the match */
+               hackline += regmatch[0].rm_eo;
+               /* flag that something has changed */
+               altered++;
 
-               case 'c':
-                       fputs(sed_cmd->editline, stdout);
-                       altered++;
+               /* if we're not doing this globally, get out now */
+               if (!sed_cmd->sub_g)
                        break;
        }
 
+       puts(hackline);
+
+       /* cleanup */
+       free(regmatch);
+
        return altered;
 }
 
+
 static void process_file(FILE *file)
 {
        char *line = NULL;
        static int linenum = 0; /* GNU sed does not restart counting lines at EOF */
        unsigned int still_in_range = 0;
-       int line_altered;
+       int altered;
        int i;
 
        /* go through every line in the file */
        while ((line = get_line_from_file(file)) != NULL) {
 
+               chomp(line);
                linenum++;
-               line_altered = 0;
+               altered = 0;
 
                /* for every line, go through all the commands */
                for (i = 0; i < ncmds; i++) {
 
-                       /* are we acting on a range of matched lines? */
-                       if (sed_cmds[i].beg_match && sed_cmds[i].end_match) {
-                               if (still_in_range || regexec(sed_cmds[i].beg_match, line, 0, NULL, 0) == 0) {
-                                       line_altered += do_sed_command(&sed_cmds[i], line);
-                                       still_in_range = 1; 
-                                       if (regexec(sed_cmds[i].end_match, line, 0, NULL, 0) == 0)
-                                               still_in_range = 0;
-                               }
-                       }
 
-                       /* are we trying to match a single line? */
-                       else if (sed_cmds[i].beg_match) {
-                               if (regexec(sed_cmds[i].beg_match, line, 0, NULL, 0) == 0)
-                                       line_altered += do_sed_command(&sed_cmds[i], line);
-                       }
+                       /*
+                        * entry point into sedding...
+                        */
+                       if (
+                                       /* no range necessary */
+                                       (sed_cmds[i].beg_line == 0 && sed_cmds[i].end_line == 0 &&
+                                        sed_cmds[i].beg_match == NULL &&
+                                        sed_cmds[i].end_match == NULL) ||
+                                       /* this line number is the first address we're looking for */
+                                       (sed_cmds[i].beg_line && (sed_cmds[i].beg_line == linenum)) ||
+                                       /* this line matches our first address regex */
+                                       (sed_cmds[i].beg_match && (regexec(sed_cmds[i].beg_match, line, 0, NULL, 0) == 0)) ||
+                                       /* we are currently within the beginning & ending address range */
+                                       still_in_range
+                          ) {
+
+                               /*
+                                * actual sedding
+                                */
+                               switch (sed_cmds[i].cmd) {
+
+                                       case 'p':
+                                               puts(line);
+                                               break;
+
+                                       case 'd':
+                                               altered++;
+                                               break;
+
+                                       case 's':
+
+                                               /*
+                                                * Some special cases for 's' printing to make it compliant with
+                                                * GNU sed printing behavior (aka "The -n | s///p Matrix"):
+                                                *
+                                                *    -n ONLY = never print anything regardless of any successful
+                                                *    substitution
+                                                *
+                                                *    s///p ONLY = always print successful substitutions, even if
+                                                *    the line is going to be printed anyway (line will be printed
+                                                *    twice).
+                                                *
+                                                *    -n AND s///p = print ONLY a successful substitution ONE TIME;
+                                                *    no other lines are printed - this is the reason why the 'p'
+                                                *    flag exists in the first place.
+                                                */
+
+                                               /* if the user specified that they didn't want anything printed (i.e., a -n
+                                                * flag and no 'p' flag after the s///), then there's really no point doing
+                                                * anything here. */
+                                               if (be_quiet && !sed_cmds[i].sub_p)
+                                                       break;
+
+                                               /* we print the line once, unless we were told to be quiet */
+                                               if (!be_quiet)
+                                                       altered |= do_subst_command(&sed_cmds[i], line);
+
+                                               /* we also print the line if we were given the 'p' flag
+                                                * (this is quite possibly the second printing) */
+                                               if (sed_cmds[i].sub_p)
+                                                       altered |= do_subst_command(&sed_cmds[i], line);
+
+                                               break;
+
+                                       case 'a':
+                                               puts(line);
+                                               fputs(sed_cmds[i].editline, stdout);
+                                               altered++;
+                                               break;
+
+                                       case 'i':
+                                               fputs(sed_cmds[i].editline, stdout);
+                                               break;
+
+                                       case 'c':
+                                               /* single-address case */
+                                               if (sed_cmds[i].end_match == NULL && sed_cmds[i].end_line == 0) {
+                                                       fputs(sed_cmds[i].editline, stdout);
+                                               }
+                                               /* multi-address case */
+                                               else {
+                                                       /* matching text */
+                                                       if (sed_cmds[i].end_match && (regexec(sed_cmds[i].end_match, line, 0, NULL, 0) == 0))
+                                                               fputs(sed_cmds[i].editline, stdout);
+                                                       /* matching line numbers */
+                                                       if (sed_cmds[i].end_line > 0 && sed_cmds[i].end_line == linenum)
+                                                               fputs(sed_cmds[i].editline, stdout);
+                                               }
+                                               altered++;
+
+                                               break;
+
+                                       case 'r': {
+                                                                 FILE *outfile;
+                                                                 puts(line);
+                                                                 outfile = fopen(sed_cmds[i].filename, "r");
+                                                                 if (outfile)
+                                                                         print_file(outfile);
+                                                                 /* else if we couldn't open the output file,
+                                                                  * no biggie, just don't print anything */
+                                                                 altered++;
+                                                         }
+                                                         break;
+                               }
 
-                       /* are we acting on a range of line numbers? */
-                       else if (sed_cmds[i].beg_line > 0 && sed_cmds[i].end_line > 0) {
-                               if (linenum >= sed_cmds[i].beg_line && linenum <= sed_cmds[i].end_line)
-                                       line_altered += do_sed_command(&sed_cmds[i], line);
-                       }
+                               /*
+                                * exit point from sedding...
+                                */
+                               if (
+                                       /* this is a single-address command or... */
+                                       (sed_cmds[i].end_line == 0 && sed_cmds[i].end_match == NULL) || (
+                                               /* we were in the middle of our address range (this
+                                                * isn't the first time through) and.. */
+                                               (still_in_range == 1) && (
+                                                       /* this line number is the last address we're looking for or... */
+                                                       (sed_cmds[i].end_line && (sed_cmds[i].end_line == linenum)) ||
+                                                       /* this line matches our last address regex */
+                                                       (sed_cmds[i].end_match && (regexec(sed_cmds[i].end_match, line, 0, NULL, 0) == 0))
+                                               )
+                                       )
+                               ) {
+                                       /* we're out of our address range */
+                                       still_in_range = 0;
+                               }
 
-                       /* are we acting on a specified line number */
-                       else if (sed_cmds[i].beg_line > 0) {
-                               if (linenum == sed_cmds[i].beg_line)
-                                       line_altered += do_sed_command(&sed_cmds[i], line);
+                               /* didn't hit the exit? then we're still in the middle of an address range */
+                               else {
+                                       still_in_range = 1;
+                               }
                        }
-
-                       /* not acting on matches or line numbers. act on every line */
-                       else 
-                               line_altered += do_sed_command(&sed_cmds[i], line);
-
                }
 
                /* we will print the line unless we were told to be quiet or if the
-                * line was altered (via a 'd'elete or 's'ubstitution) */
-               if (!be_quiet && !line_altered)
-                       fputs(line, stdout);
+                * line was altered (via a 'd'elete or 's'ubstitution), in which case
+                * the altered line was already printed */
+               if (!be_quiet && !altered)
+                       puts(line);
 
                free(line);
        }
@@ -551,28 +741,15 @@ extern int sed_main(int argc, char **argv)
 {
        int opt;
 
-       /* do special-case option parsing */
-       if (argv[1] && (strcmp(argv[1], "--help") == 0))
-               usage(sed_usage);
-
-#if 0
+#ifdef BB_FEATURE_CLEAN_UP
        /* destroy command strings on exit */
-       if (atexit(destroy_cmd_strs) == -1) {
-               perror("sed");
-               exit(1);
-       }
+       if (atexit(destroy_cmd_strs) == -1)
+               perror_msg_and_die("atexit");
 #endif
 
        /* do normal option parsing */
-       while ((opt = getopt(argc, argv, "Vhne:f:")) > 0) {
+       while ((opt = getopt(argc, argv, "ne:f:")) > 0) {
                switch (opt) {
-                       case 'V':
-                               printf("BusyBox v%s (%s)\n", BB_VER, BB_BT);
-                               exit(0);
-                               break;
-                       case 'h':
-                               usage(sed_usage);
-                               break;
                        case 'n':
                                be_quiet++;
                                break;
@@ -582,6 +759,8 @@ extern int sed_main(int argc, char **argv)
                        case 'f': 
                                load_cmd_file(optarg);
                                break;
+                       default:
+                               show_usage();
                }
        }
 
@@ -589,7 +768,7 @@ extern int sed_main(int argc, char **argv)
         * argv[optind] should be the pattern. no pattern, no worky */
        if (ncmds == 0) {
                if (argv[optind] == NULL)
-                       usage(sed_usage);
+                       show_usage();
                else {
                        add_cmd_str(argv[optind]);
                        optind++;
@@ -609,7 +788,7 @@ extern int sed_main(int argc, char **argv)
                for (i = optind; i < argc; i++) {
                        file = fopen(argv[i], "r");
                        if (file == NULL) {
-                               fprintf(stderr, "sed: %s: %s\n", argv[i], strerror(errno));
+                               perror_msg("%s", argv[i]);
                        } else {
                                process_file(file);
                                fclose(file);