BASIC-DOS

SED

SED [/I] [/N] script [file]

A filter that runs the commands in script on each line of input (or file), and then displays the line, unless /N is given, like a simple version of the UNIX sed command (eg, DIR | SED s/BAS/BAK/).

• /I ignores case when matching
• /N displays only what the commands display

As with FIND’s string, script needs quotes only if it contains spaces or starts with the switch character (eg, DIR | SED "/^D/d"), and it can be a string variable. Also quote the script if it contains other characters that BASIC-DOS treats specially (eg, |, >, :, or '); it can’t contain a double quote.

Commands

The commands in a script are separated by semicolons, and each has the form:

[address[,address]][!]command

A command with no address applies to every line, a command with one address applies to each line that the address selects, and a command with two applies to each range of lines, from a line that the first address selects through the next line that the second selects (or just the one line, if the second address is a line number that’s already been reached). A ! applies the command to the lines that aren’t selected instead. An address is:

• n: line n (the first line is 1)
• $: the last line
• /regex/: each line that the regular expression regex matches

The commands are:

• s/regex/text/[g][p]: replaces the first match of regex with text, or with g, every match (eg, s/ */ /g changes each run of spaces to one space); in text, & is the match, \1 through \9 are the parts of the match that \( and \) marked in regex, and \ makes any other character ordinary (eg, \& or \\). With p, the line is displayed if anything was replaced. Any character can be used instead of / (eg, s,/,\\,g replaces each / with \).
• d: deletes the line (skipping the rest of the commands)
• p: displays the line
• q: quits, after displaying the line (unless /N was given)
• =: displays the line number

Examples

SED 10q README.TXT                   displays the first 10 lines
SED /N "$=" README.TXT               displays the number of lines
SED /N "/BASIC/p" README.TXT         displays the lines containing "BASIC"
SED "/^$/d" README.TXT               removes empty lines
SED "s/\(.*\)=\(.*\)/\2=\1/" X.TXT   swaps the two sides of each "="
SED "1,/^$/d" MAIL.TXT               removes the lines through the first empty one

Limits and Messages

As in every filter, a line longer than 254 characters is split, and if an s command would make a line longer than that, the extra characters are dropped. A script is limited to what fits on a command line.

ERRORLEVEL is set to 0, or 2 if a switch isn’t valid or script is missing (Syntax error), script is invalid (Invalid script), or file couldn’t be opened (eg, Unable to find X.TXT).

Source: sed.asm

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