Editor - Line extractor
lineextractor, linext, lex
lex [ <options> ] " [<start_bounder>] <n> [<end_bounder>] " <input_string>
-p Preserve the input string. Without this option, when
a part of the input string (called the extraction target,
or just target) is extracted, that part is removed from
the input string. (This is done so that each subsequent
extract command will produce subsequent lines.) With this
option, the input string is left unchanged.
-e Count and return empty strings. This option is useful, for example, if you
have records separated by newlines in a file, and you want to receive empty records.
-c Case insensitive. Case will be ignored when considering separator characters.
The input string on which this command will operate. It
can be specified as a str constant or str variable or an
expression resulting in a str value.
If a str constant is used, we highly recommend using
double quotes around it, such as "John Doe".
Without the double quotes, the spaces in the input string
will produce errors. In case of a str constant or a str
expression, the -p option is assumed.
<n> The instance number (line number). The input string will be searched for this
instance of the target. Instances are counted from 1.
<n> must be either a number higher than 0 or the letter l (which indicates
the last instance).
This argument can either be absent, the character [ or the character ].
The <start_bounder> appears before the <n>. The <end_bounder>
appears after the <n>.
We will now explain the role of these bounders with an example.
We will assume that we are looking for fifth line.
"5" Extract only the fifth line.
"5[" Extract everything after but excluding the fifth line.
"5]" Extract everything upto and including the fifth line.
"[5" Extract everything beginning with and including the fifth line.
"[5[" This combination is INVALID.
"" Extract only the fifth line. This is same as "5".
"]5" Extract everything upto but excluding the fifth line.
"]5[" Extract everything outside but excluding the fifth line.
"]5]" This combination is INVALID.
The quotes in the command syntax are required. Without the double quotes, an error
or erroneous output may be produced.
Stream input is ignored.
The extracted content is added to stream output.
Any errors are listed here.
The command extracts the target line(s) from the input string and writes them to
the stream output or redirected output target. If <input_string> is a constant or an expression,
it remains unchanged. If <input_string> is a variable, and if the -p option is not
specified, the target is removed from the <input_string>. Similarly, if <input_string>
is a variable, and if the -p option is specified, the <input_string> remains unchanged.
The command CAN ALSO BE USED WITH FILES. Simply read in the contents
of the file using the repro command into a str variable. The following is
an example. Assume that we want to operate the lex command on file "My Code.java".
var str s
repro "My Code.java" > $s
# Do something with $s using the lex command.
# Then write the input string back to the file.
echo $s > "My Code.aspx"
The following system variable plays an important role.
$lsep Line separator
Each character in $lsep is considered to be a line separator.
This variable is used to identify, number, and extract distinct lines.
See the 'systemvar' help topic for its description.
You can change its value to highly refine your search procedure.
We highly recommend that, if you change any system variable's value, you restore it
after the search is complete, as many system variables are often
used by more than one command. This restoration can be done using code
similar to the following.
# Save the original $lsep.
var str saved_lsep
set $saved_lsep = $lsep
# Restore the original value of $lsep.
set $lsep = $saved_lsep
# Good job !
If the <input_string> is specified as a constant or as a str expression,
the presence or absence of option -p is ignored. A constant never changes its value.
The following example reverses lines in a file. Assume the file name is in
var str $fileName
# Assign value of $fileName
var str content
var str line
repro $fileName > $content
while ($content <> "")
# Extract the last line. Allow empty.
lex -e "l" $content > $line # Note we are using Ell (l) for last line.
var str s
# Assign value to $s
lex 1[ $s # Extract every thing after first line.
Will produce erroneous output. 1[ must be enclosed in double quotes as "1[". It can however be
also passed as a variable. The following code shows that.
Let's say you don't know the line number you want to extract up-front. You have it
available only in a variable $num.
var str s
var int num
# Value of num and s are set.
# We will create a variable for passing as argument to the lex command.
var str lex_arg
set $lex_arg = makestr(int($num)) # We are converting $num to str.
set $lex_arg = $lex_arg+"[" # Should result in "1[", "5[", etc.
lex $lex_arg $s # Will correctly extract parts of s after (and excluding) line number $num.
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