Hi! Per Issue 8 Draft 2.1 (XCU, csplit, OPERANDS): 84808 Each arg operand can be one of the following:
84809 /rexp/[offset]
84810 A file shall be created using the content of the lines from the current
line up to, but
84811 not including, the line that results from the evaluation of the regular
expression
84812 with offset, if any, applied. The regular expression rexp shall follow
the rules for
84813 basic regular expressions described in XBD Section 9.3 (on page 167).
The
84814 application shall use the sequence "\/" to specify a <slash> character
within the
84815 rexp. The optional offset shall be a positive or negative integer value
representing a
84816 number of lines. A positive integer value can be preceded by '+'. If
the selection
84817 of lines from an offset expression of this type would create a file
with zero lines, or
84818 one with greater than the number of lines left in the input file, the
results are
84819 unspecified. After the section is created, the current line shall be
set to the line that
84820 results from the evaluation of the regular expression with any offset
applied. If the
84821 current line is the first line in the file and a regular expression
operation has not yet
84822 been performed, the pattern match of rexp shall be applied from the
current line to
84823 the end of the file. Otherwise, the pattern match of rexp shall be
applied from the
84824 line following the current line to the end of the file.
84825 %rexp%[offset]
84826 Equivalent to /rexp/[offset], except that no file shall be created for
the selected
84827 section of the input file. The application shall use the sequence "\%"
to specify a
84828 <percent-sign> character within the rexp.
Per XBD 9.3.8:
6011 9.3.8 BRE Expression Anchoring
6012 A BRE can be limited to matching expressions that begin or end a
string; this is called
6013 ``anchoring’’. The <circumflex> and <dollar-sign> special characters
shall be considered BRE
6014 anchors in the following contexts:
...
6023 2. A <dollar-sign> ('$') shall be an anchor when used as the last
character of an entire BRE.
6024 The implementation may treat a <dollar-sign> as an anchor when used as
the last
6025 character of a subexpression. The <dollar-sign> shall anchor the
expression (or optionally
6026 subexpression) to the end of the string being matched; the
<dollar-sign> can be said to
6027 match the end-of-string following the last character.
6028 3. A BRE anchored by both '^' and '$' shall match only an entire
string. For example, the
6029 BRE "^abcdef$" matches strings consisting only of "abcdef".
So, naturally, for this:
$ echo 10 | csplit - '/^10$/'
XCU, csplit, OPERANDS again:
84836 An error shall be reported if an operand does not reference a line
between the current position
84837 and the end of the file.
Since a line is, as we all know, defined as (XBD):
1721 3.179 Line
1722 A sequence of zero or more non-<newline> characters plus a terminating
<newline> character.
And, naturally, the regex doesn't match the end of the line.
Conversely, the following must work:
$ echo 10 | csplit - '/^10
$/'
Behold (I've substituted echo for seq because NetBSD csplit has issues
when presented with just one line):
netbsd-9.2$ seq 999 | csplit - '/^10$/'
csplit: ^10$: no match
netbsd-9.2$ seq 999 | csplit - '/^10
$/'
18
3870
netbsd-9.2$ wc -l *
9 xx00
990 xx01
990 total
vs (coreutils 8.32-4+b1 and 9.1-1):
debian$ seq 999 | csplit - '/^10$/'
18
3870
debian$ wc -l *
9 xx00
990 xx01
999 total
debian$ seq 999 | csplit - '/^10
$/'
csplit: ‘/^10\n$/’: match not found
3888
FreeBSD agrees with NetBSD.
The illumos gate (5.11; tribblix m25) agrees with coreutils.
From the user's stand-point, it doesn't seem to make sense to require
specifying the newline literally, since the input is defined to consist
of lines only /anyway/.
Might it make sense to spec that the rexps are to be compiled with
REG_NEWLINE, or the equivalent?
Best,
наб
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