Is it possible to encapsulate the following pseudocode using sed?
for line in lines:
if line == "foo":
print "FOO"
else:
print "- " + line
Here's the first thing I tried:
> echo 'foo
> bar
> baz' | sed -e 's/^foo$/FOO/' -e 's/^/- /'
- FOO
- bar
- baz
This is incorrect since both substitutions are applied to the first line.
Is it possible to tell sed to perform a maximum of one substitution per line?
You can limit what lines a substitution affects, by prefixing it with a pattern:
sed -e '/^foo$/! s/^/- /' -e '/^foo$/ s//FOO/' infile
A better alternative is to use the t branch command which will go to the next line if the previous substitution succeeded:
sed 's/^foo$/FOO/; t; s/^/- /' infile
Or the more portable:
sed -e 's/^foo$/FOO/' -e t -e 's/^/- /' infile
Output in both cases:
FOO
- bar
- baz
Related
To delete/comment 3 lines befor a pattern (including the line with the pattern):
how can i achive it through sed command
Ref:
sed or awk: delete n lines following a pattern
the above ref blog help to achive the this with after a pattern match but i need to know before match
define host{
use xxx;
host_name pattern;
alias yyy;
address zzz;
}
the below sed command will comment the '#' after the pattern match for example
sed -e '/pattern/,+3 s/^/#/' file.cfg
define host{
use xxx;
#host_name pattern;
#alias yyy;
#address zzz;
#}
like this how can i do this for the before pattern?
can any one help me to resolve this
If tac is allowed :
tac|sed -e '/pattern/,+3 s/^/#/'|tac
If tac isn't allowed :
sed -e '1!G;h;$!d'|sed -e '/pattern/,+3 s/^/#/'|sed -e '1!G;h;$!d'
(source : http://sed.sourceforge.net/sed1line.txt)
Reverse the file, comment the 3 lines after, then re-reverse the file.
tac file | sed '/pattern/ {s/^/#/; N; N; s/\n/&#/g;}' | tac
#define host{
#use xxx;
#host_name pattern;
alias yyy;
address zzz;
}
Although I think awk is a little easier to read:
tac file | awk '/pattern/ {c=3} c-- > 0 {$0 = "#" $0} 1' | tac
This might work for you (GNU sed):
sed ':a;N;s/\n/&/3;Ta;/pattern[^\n]*$/s/^/#/mg;P;D' file
Gather up 4 lines in the pattern space and if the last line contains pattern insert # at the beginning of each line in the pattern space.
To delete those 4 lines, use:
sed ':a;N;s/\n/&/3;Ta;/pattern[^\n]*$/d;P;D' file
To delete the 3 lines before pattern but not the line containing pattern use:
sed ':a;N;s/\n/&/3;Ta;/pattern[^\n]*$/s/.*\n//;P;D'
I am trying replace a block of code between two patterns with blank lines
Tried using below command
sed '/PATTERN-1/,/PATTERN-2/d' input.pl
But it only removes the lines between the patterns
PATTERN-1 : "=head"
PATTERN-2 : "=cut"
input.pl contains below text
=head
hello
hello world
world
morning
gud
=cut
Required output :
=head
=cut
Can anyone help me on this?
$ awk '/=cut/{f=0} {print (f ? "" : $0)} /=head/{f=1}' file
=head
=cut
To modify the given sed command, try
$ sed '/=head/,/=cut/{//! s/.*//}' ip.txt
=head
=cut
//! to match other than start/end ranges, might depend on sed implementation whether it dynamically matches both the ranges or statically only one of them. Works on GNU sed
s/.*// to clear these lines
awk '/=cut/{found=0}found{print "";next}/=head/{found=1}1' infile
# OR
# ^ to take care of line starts with regexp
awk '/^=cut/{found=0}found{print "";next}/^=head/{found=1}1' infile
Explanation:
awk '/=cut/{ # if line contains regexp
found=0 # set variable found = 0
}
found{ # if variable found is nonzero value
print ""; # print ""
next # go to next line
}
/=head/{ # if line contains regexp
found=1 # set variable found = 1
}1 # 1 at the end does default operation
# print current line/row/record
' infile
Test Results:
$ cat infile
=head
hello
hello world
world
morning
gud
=cut
$ awk '/=cut/{found=0}found{print "";next}/=head/{found=1}1' infile
=head
=cut
This might work for you (GNU sed):
sed '/=head/,/=cut/{//!z}' file
Zap the lines between =head and =cut.
Problem statement:
change every user agent that does not match A2PC or GENCOM with the user agent PROHIBITED and keep GENCOM and A2PC unchanged
Expression:
echo \"GENCOM\" | sed -r -e 's/(^((?!A2PC)(?!GENCOM).)*$)/PROHIBITED/g'
error:
sed: -e expression #1, char 41: Invalid preceding regular expression
I removed -r then error not thrown but its not working
echo \"GENDFGGH\" | sed -e 's/(^((?!A2PC)(?!GENCOM).)*$)/PROHIBITED/g'
"GENDFGGH"
Please help me for this solution
First look for your pattern and then do the sub:
# echo \"GENCsOM\" | sed -e '/^"\(GENCOM\|A2PC\)"$/! s/^.*$/PROHIBITED/'
PROHIBITED
# echo \"GENCOM\" | sed -e '/^"\(GENCOM\|A2PC\)"$/! s/^.*$/PROHIBITED/'
"GENCOM"
sed '/A2PC/ !{
/GENCOM/ ! {
s/$/PROHIBITED/
}
}' YourFile
double exclusion than a change, posix compliant
I have a special file with this kind of format :
title1
_1 texthere
title2
_2 texthere
I would like all newlines starting with "_" to be placed as a second column to the line before
I tried to do that using sed with this command :
sed 's/_\n/ /g' filename
but it is not giving me what I want to do (doing nothing basically)
Can anyone point me to the right way of doing it ?
Thanks
Try following solution:
In sed the loop is done creating a label (:a), and while not match last line ($!) append next one (N) and return to label a:
:a
$! {
N
b a
}
After this we have the whole file into memory, so do a global substitution for each _ preceded by a newline:
s/\n_/ _/g
p
All together is:
sed -ne ':a ; $! { N ; ba }; s/\n_/ _/g ; p' infile
That yields:
title1 _1 texthere
title2 _2 texthere
If your whole file is like your sample (pairs of lines), then the simplest answer is
paste - - < file
Otherwise
awk '
NR > 1 && /^_/ {printf "%s", OFS}
NR > 1 && !/^_/ {print ""}
{printf "%s", $0}
END {print ""}
' file
This might work for you (GNU sed):
sed ':a;N;s/\n_/ /;ta;P;D' file
This avoids slurping the file into memory.
or:
sed -e ':a' -e 'N' -e 's/\n_/ /' -e 'ta' -e 'P' -e 'D' file
A Perl approach:
perl -00pe 's/\n_/ /g' file
Here, the -00 causes perl to read the file in paragraph mode where a "line" is defined by two consecutive newlines. In your example, it will read the entire file into memory and therefore, a simple global substitution of \n_ with a space will work.
That is not very efficient for very large files though. If your data is too large to fit in memory, use this:
perl -ne 'chomp;
s/^_// ? print "$l " : print "$l\n" if $. > 1;
$l=$_;
END{print "$l\n"}' file
Here, the file is read line by line (-n) and the trailing newline removed from all lines (chomp). At the end of each iteration, the current line is saved as $l ($l=$_). At each line, if the substitution is successful and a _ was removed from the beginning of the line (s/^_//), then the previous line is printed with a space in place of a newline print "$l ". If the substitution failed, the previous line is printed with a newline. The END{} block just prints the final line of the file.
I have a file which looks like below:
memory=500G
brand=HP
color=black
battery=5 hours
For every line, I want to remove everything after = and also the =.
Eventually, I want to get something like:
memory:brand:color:battery:
(All on one line with colons after every word)
Is there a one-line sed command that I can use?
sed -e ':a;N;$!ba;s/=.\+\n\?/:/mg' /my/file
Adapted from this fine answer.
To be frank, however, I'd find something like this more readable:
cut -d = -f 1 /my/file | tr \\n :
Here's one way using GNU awk:
awk -F= '{ printf "%s:", $1 } END { printf "\n" }' file.txt
Result:
memory:brand:color:battery:
If you don't want a colon after the last word, you can use GNU sed like this:
sed -n 's/=.*//; H; $ { g; s/\n//; s/\n/:/g; p }' file.txt
Result:
memory:brand:color:battery
This might work for you (GNU sed):
sed -i ':a;$!N;s/=[^\n]*\n\?/:/;ta' file
perl -F= -ane '{print $F[0].":"}' your_file
tested below:
> cat temp
abc=def,100,200,dasdas
dasd=dsfsf,2312,123,
adasa=sdffs,1312,1231212,adsdasdasd
qeweqw=das,13123,13,asdadasds
dsadsaa=asdd,12312,123
> perl -F= -ane '{print $F[0].":"}' temp
abc:dasd:adasa:qeweqw:dsadsaa:
My command is
First step:
sed 's/([a-z]+)(\=.*)/\1:/g' Filename |cat >a
cat a
memory:
brand:
color:
battery:
Second step:
sed -e 'N;s/\n//' a | sed -e 'N;s/\n//'
My output is
memory:brand:color:battery: