I'm trying to create a script to append oracleserver to /etc/hosts as an alias of localhost. Which means I need to:
Locate the line that ^127.0.0.1 and NOT oracleserver$
Then, append oracleserver to this line
I know the best practice is probably using negative look ahead. However, sed does not have look around feature: What's wrong with my lookahead regex in GNU sed?. Can anyone provide me some possible solutions?
sed -i '/oracleserver$/! s/^127\.0\.0\.1.*$/& oracleserver/' filename
/oracleserver$/! - on lines not ending with oracleserver
^127\.0\.0\.1.*$ - replace the whole line if it is starting with 127.0.0.1
& oracleserver - with the line plus a space separator ' ' (required) and oracleserver after that
Just use awk with && to combine the two conditions:
awk '/^127\.0\.0\.1/ && !/oracleserver$/ { $0 = $0 "oracleserver" } 1' file
This appends the string when the first pattern is matched but the second one isn't. The 1 at the end is always true, so awk prints each line (the default action is { print }).
I wouldn't use sed but instead perl:
Locate the line that ^127.0.0.1 and NOT oracleserver$
perl -pe 'if ( m/^127\.0\.0\.1/ and not m/oracleserver$/ ) { s/$/oracleserver/ }'
Should do the trick. You can add -i.bak to inplace edit too.
Related
If I have the string:
geo:FR, host:www.example.com
(In reality the string is more complicated and has more fields.)
And I want to extract the "geo" value and the "host" value, I am facing a problem when the order of the keys change, as in the following:
host:www.example.com, geo:FR
I tried this line:
sed 's/.\*geo:\([^ ]*\).\*host:\([^ ]*\).*/\1,\2/'
But it only works on the first string.
Is there a way to do it in a single regex, and if not, what's the best approach?
I suggest extracting each text you need with a separate sed command:
s="geo:FR, host:www.example.com"
host="$(sed -n 's/.*host:\([^[:space:],]*\).*/\1/p' <<< "$s")"
geo="$(sed -n 's/.*geo:\([^[:space:],]*\).*/\1/p' <<< "$s")"
See the online demo, echo "$host and $geo" prints
www.example.com and FR
for both inputs.
Details
-n suppresses line output and p prints the matches
.* - matches any 0+ chars up the last...
host: - host: substring and then
\([^[:space:],]*\) - captures into Group 1 any 0 or more chars other than whitespace and a comma
.* - the rest of the line.
The result is just the contents of Group 1 (see \1 in the replacement pattern).
Whenever you have tag/name to value pairs in your input I find it best (clearest, simplest, most robust,, easiest to enhance, etc.) to first create an array that contains that mapping (f[] below) and then you can simply access the values by their tags:
$ cat file
geo:FR, host:www.example.com
host:www.example.com, geo:FR
foo:bar, host:www.example.com, stuff:nonsense, badgeo:uhoh, geo:FR, nastygeo:wahwahwah
$ cat tst.awk
BEGIN { FS=":|, *"; OFS="," }
{
for (i=1; i<=NF; i+=2) {
f[$i] = $(i+1)
}
print f["geo"], f["host"]
}
$ awk -f tst.awk file
FR,www.example.com
FR,www.example.com
FR,www.example.com
The above will work using any awk in any shell on every UNIX box.
Here I've used GNU Awk to convert your delimited key:value pairs to valid shell assignment. With Bash, you can load these assignments into your current shell using <(process substitution):
# source the file descriptor generated by proc sub
. < <(
# use comma-space as field separator, literal apostrophe as variable q
awk -F', ' -vq=\' '
# change every foo:bar in line to foo='bar' on its own line
{for(f=1;f<=NF;f++) print gensub(/:(.*)/, "=" q "\\1" q, 1, $f)}
# use here-string to load text; remove everything but first quote to use standard input
' <<< 'host:www.example.com, geo:FR'
)
How can I use sed to add a dynamic prefix to each number in an integer list?
For example:
I have a string "A-1,2,3,4,5", I want to transform it to string "A-1,A-2,A-3,A-4,A-5" - which means I want to add prefix of first integer i.e. "A-" to each number of the list.
If I have string like "B-1,20,300" then I want to transform it to string "B-1,B-20,B-300".
I am not able to use RegEx Capturing Groups because for global match they do not retain their value in subsequent matches.
When it comes to looping constructs in sed, I like to use newlines as markers for the places I have yet to process. This makes matching much simpler, and I know they're not in the input because my input is a text line.
For example:
$ echo A-1,2,3,4,5 | sed 's/,/\n/g;:a s/^\([^0-9]*\)\([^\n]*\)\n/\1\2,\1/; ta'
A-1,A-2,A-3,A-4,A-5
This works as follows:
s/,/\n/g # replace all commas with newlines (insert markers)
:a # label for looping
s/^\([^0-9]*\)\([^\n]*\)\n/\1\2,\1/ # replace the next marker with a comma followed
# by the prefix
ta # loop unless there's nothing more to do.
The approach is similar to #potong's, but I find the regex much more readable -- \([^0-9]*\) captures the prefix, \([^\n]*\) captures everything up to the next marker (i.e. everything that's already been processed), and then it's just a matter of reassembling it in the substitution.
Don't use sed, just use the other standard UNIX text manipulation tool, awk:
$ echo 'A-1,2,3,4,5' | awk '{p=substr($0,1,2); gsub(/,/,"&"p)}1'
A-1,A-2,A-3,A-4,A-5
$ echo 'B-1,20,300' | awk '{p=substr($0,1,2); gsub(/,/,"&"p)}1'
B-1,B-20,B-300
This might work for you (GNU sed):
sed -E ':a;s/^((([^-]+-)[^,]+,)+)([0-9])/\1\3\4/;ta' file
Uses pattern matching and a loop to replace a number following a comma by the first column prefix and that number.
Assuming this is for shell scripting, you can do so with 2 seds:
set string = "A1,2,3,4,5"
set prefix = `echo $string | sed 's/^\([A-Z]\).*/\1/'`
echo $string | sed 's/,\([0-9]\)/,'$prefix'-\1/g'
Output is
A1,A-2,A-3,A-4,A-5
With
set string = "B-1,20,300"
Output is
B-1,B-20,B-300
Could you please try following(if ok with awk).
awk '
BEGIN{
FS=OFS=","
}
{
for(i=1;i<=NF;i++){
if($i !~ /^A/&&$i !~ /\"A/){
$i="A-"$i
}
}
}
1' Input_file
if your data in 'd' file, tried on gnu sed:
sed -E 'h;s/^(\w-).+/\1/;x;G;:s s/,([0-9]+)(.*\n(.+))/,\3\1\2/;ts; s/\n.+//' d
I am trying to code a bash script in a build process where we only have a few tools (like grep, sed, awk) and I am trying to replace a value in an ini file with a value from a regular expression match in another.
So, I am matching something like "^export ADDRESS=VALUE" in file export_vars.h and putting VALUE into an ini file called config.ini in a line with "ADDRESS=[REPLACE]". So, I am trying to replace [REPLACE] with VALUE with one command in bash.
I have come across that sed can take an entire file and insert it into another with a command like
sed -i -e "/[REPLACE]/r export_vars.h" config.ini
I need to somehow refine this command to only read the pattern match from export_vars.h. Does anyone know how to do this?
sed is for simple substitutions on individual lines, that is all. You need to be looking at awk for what you're trying to do. Something like:
awk '
BEGIN { FS=OFS="=" }
NR==FNR {
if ( $1 == "export ADDRESS" ) {
value = $2
}
next
}
{ sub(/\[REPLACE\]/,value); print }
' export_vars.h config.ini
Untested, of course, since you didn't provide testable sample input/output.
Another in awk:
$ awk '/ADDRESS/{if(a!="")$0=a;else a=$NF}NR>FNR' export_vars.h config.ini
ADDRESS=VALUE
Explained:
$ awk '
/ADDRESS/ { # when ADDRESS is found in record
if(a!="") $0=a # if a is set (from first file), use it
else a=$NF } # otherwise set a with the last field
NR>FNR # print all record of the last file
' export_vars.h config.ini # mind the order
This solution does not tolerate space around = since $0 is replaced with $NF from the other file.
is there a way to do this kind of substitution in Awk, sed, ...?
I have a text file with sections divived into two blank lines;
section1_name_x
dklfjsdklfjsldfjsl
section2_name_x
dlskfjsdklfjsldkjflkj
section_name_X
dfsdjfksdfsdf
I would to replace every "section_name_x" by "#section_name_x", this is, how to replace the next string after match (every) two blank lines?
Thanks,
Steve,
awk '
(NR==1 || blank==2) && $1 ~ /^section/ {sub(/section/, "#&")}
{
print
if (length)
blank = 0
else
blank ++
}
' file
#section1_name_x
dklfjsdklfjsldfjsl
#section2_name_x
dlskfjsdklfjsldkjflkj
#section_name_X
dfsdjfksdfsdf
hm....
Given your example data why not just
sed 's/^section[0-9]*_name.*/#/' file > newFile && mv newFile file
some seds support sed -i OR sed -i"" to overwrite the existing file, avoiding the && mv ... shown above.
The reg ex says, section must be at the beginning of the line, and can optionally contain a number or NO number at all.
IHTH
In gawk you can use the RT builtin variable:
gawk '{$1="#"$1; print $0 RT}' RS='\n\n' file
* Update *
Thanks to #EdMorton I realized that my first version was incorrect.
What happens:
Assigning to $1 causes the record to be rebuildt, which is not good in this cases since any sequence of white space is replaced by a single space between fields, and by the null string in the beginning and at the end of the record.
Using print adds an additional newline to the output.
The correct version:
gawk '{printf "%s", "#" $0 RT}' RS='\n\n\n' file
I have a pattern like
Fixed pattern
text which can change(world)
I want to replace this with
Fixed pattern
text which can change(hello world)
What I am trying to use
cat myfile | sed -e "s#\(Fixed Pattern$A_Z_a_z*\(\)#\1 hello#g > newfile
UPDATE:
The above word world is also a variable and will change
Basically add hello after the first parenthesis encountered after the expression.
Thanks in advance.
Assuming your goal is to add 'hello ' inside of every opening parentheses on the line after 'Fixed pattern', here is a solution that should work:
sed -e '/^Fixed pattern$/!b' -e 'n' -e 's/(/(hello /' myfile
Here is an explanation of each portion:
/^Fixed pattern$/!b # skip all of the following commands if 'Fixed pattern'
# doesn't match
n # if 'Fixed pattern' did match, read the next line
s/(/(hello / # replace '(' with '(hello '
To do this with sed, use n:
sed '/Fixed pattern/{n; s/world/hello world/}' myfile
You may need to be more careful, but this should work for most situations. Whenever sed sees the Fixed pattern (you may want to use line anchors ^ and $), it will read the next line and then apply the substitution to it.