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How do I remove the ^L character and the blank lines that come after it on a unix file? I have tried the below and have been able to remove the VT and spaces but am failing to remove the ^L character and the blank lines after it
tr -s '\040\011\' '|' <$x>> modified.txt
and:
tr -d '\013' <modified1.txt>> $FILENAME
That's the caret notation for the form feed character. With the GNU implementation of sed, you can remove it using its octal value, \o14 :
sed 's/\o14//g' file
You can also use its escape code:
sed 's/\f//' file
Such characters can be entered in the terminal by pressing CtrlV and then the code for the character. In this case, CtrlL. So, type this:
sed 's/
Then, hit CtrlV and then CtrlL:
sed 's/^L
Now, complete the command:
sed 's/^L//g' file
Don't write ^L and don't paste it from the above, use the keyboard shortcut I gave.
You could also remove it with tr:
tr -d '\f' < file
Or perl:
perl -pe 's/\f//g' file
To delete both the \f and any blank lines following it, you could do something like:
perl -0pe 's/\f\s*/\n/s' file
With ksh93, bash, zsh, mksh, recent FreeBSD sh:
sed $'/\f/,/./{/\f/d;/./!d;}'
That will fail if there are consecutive sequences of \f\n\n...s though.
With GNU sed, you can omit the $.
POSIXly ($'...' is not POSIX yet, though will probably be in SUSv5):
FF=$(printf '\f')
sed "/$FF/,/./{/$FF/d;/./!d;}"
Note that the current POSIX spec requires a newline instead of ; before }, but that's actually a bug in the POSIX spec as not even the initial implementation of sed ever required it.
$' '? Isn't it sed that deals with interpreting the escape characters? Why use the ANSI escape for them?
– terdon♦
Jul 31 '15 at 9:15
\n, none on the RHS. GNU sed supports more, though when inside [...] that depends on whether POSIXLY_CORRECT is in the environment or not.
– Stéphane Chazelas
Jul 31 '15 at 10:15
; after }, but it's fine before }). Will be fixed in the next version.
– Stéphane Chazelas
Jul 31 '15 at 10:22
sed -E thing has been Accepted as Marked since 2012 I think - I think I recall some bugs kicking about Accepted as Marked about [[ ]] since 2011 or so (could be wrong about that bit, though). I'm also looking forward to tail -r - but I can't figure out what Accepted as Marked is supposed to mean.
– mikeserv
Jul 31 '15 at 15:33
sed "$(printf '$!N;/\f')"'\n/,/\n./!P;D' <in >out
...should work provided a POSIX compliant shell, printf, and sed.
You don't really need printf though if you just insert the character literally. You can usually do it with CTRL+V then CTRL+L.
So...
sed '$!N;/^L\n/,/\n./!P;D' <in >out
...where the ^L sequence above is got by doing CTRL+V then CTRL+L and represents the literal form feed character.
printf argument. But to a POSIX sed \f is just f.
– mikeserv
Jul 31 '15 at 10:14
\f is unspecified, so any behaviour (including rebooting the computer or matching the FF or 🏭 character) by a POSIX sed implementation is allowed. [\f] is meant to match either backslash or f though. POSIX sed script that uses \f outside [] is not conformant. One that uses \f inside [...] would be but break with GNU sed (unless POSIXLY_CORRECT is on) where it would match a FF instead of backslash or f (so it's better to use sed 's/[\\f]// if you want to match on backslash or f.
– Stéphane Chazelas
Jul 31 '15 at 10:51
for E in a\\a b\\b e\\33 f\\f n\\n t\\t v\\v; do eval "${E%\\*}='$(printf "${E#?}'")"; done - puts them all in vars like $e and $n and so on. And there's no worry about escape support.
– mikeserv
Jul 31 '15 at 11:16
\014.\013is VT (vertical tab). L is the 12th letter of the English alphabet (14 in octal). – Stéphane Chazelas Jul 31 '15 at 9:23