I have variable which has value "abcd.txt".
I want to store everything before the ".txt" in a second variable, replacing the ".txt" with ".log"
I have no problem echoing the desired value:
a="abcd.txt"
echo $a | sed 's/.txt/.log/'
But how do I get the value "abcd.log" into the second variable?
You can use command substitution as:
new_filename=$(echo "$a" | sed 's/.txt/.log/')
or the less recommended backtick way:
new_filename=`echo "$a" | sed 's/.txt/.log/'`
You can use backticks to assign the output of a command to a variable:
logfile=`echo $a | sed 's/.txt/.log/'`
That's assuming you're using Bash.
Alternatively, for this particular problem Bash has pattern matching constructs itself:
stem=$(textfile%%.txt)
logfile=$(stem).log
or
logfile=$(textfile/%.txt/.log)
The % in the last example will ensure only the last .txt is replaced.
The simplest way is
logfile="${a/\.txt/\.log}"
If it should be allowed that the filename in $a has more than one occurrence of .txt in it, use the following solution. Its more safe. It only changes the last occurrence of .txt
logfile="${a%%\.txt}.log"
if you have Bash/ksh
$ var="abcd.txt"
$ echo ${var%.txt}.log
abcd.log
$ variable=${var%.txt}.log
Related
If I run these commands from a script:
#my.sh
PWD=bla
sed 's/xxx/'$PWD'/'
...
$ ./my.sh
xxx
bla
it is fine.
But, if I run:
#my.sh
sed 's/xxx/'$PWD'/'
...
$ ./my.sh
$ sed: -e expression #1, char 8: Unknown option to `s'
I read in tutorials that to substitute environment variables from shell you need to stop, and 'out quote' the $varname part so that it is not substituted directly, which is what I did, and which works only if the variable is defined immediately before.
How can I get sed to recognize a $var as an environment variable as it is defined in the shell?
Your two examples look identical, which makes problems hard to diagnose. Potential problems:
You may need double quotes, as in sed 's/xxx/'"$PWD"'/'
$PWD may contain a slash, in which case you need to find a character not contained in $PWD to use as a delimiter.
To nail both issues at once, perhaps
sed 's#xxx#'"$PWD"'#'
In addition to Norman Ramsey's answer, I'd like to add that you can double-quote the entire string (which may make the statement more readable and less error prone).
So if you want to search for 'foo' and replace it with the content of $BAR, you can enclose the sed command in double-quotes.
sed 's/foo/$BAR/g'
sed "s/foo/$BAR/g"
In the first, $BAR will not expand correctly while in the second $BAR will expand correctly.
Another easy alternative:
Since $PWD will usually contain a slash /, use | instead of / for the sed statement:
sed -e "s|xxx|$PWD|"
You can use other characters besides "/" in substitution:
sed "s#$1#$2#g" -i FILE
一. bad way: change delimiter
sed 's/xxx/'"$PWD"'/'
sed 's:xxx:'"$PWD"':'
sed 's#xxx#'"$PWD"'#'
maybe those not the final answer,
you can not known what character will occur in $PWD, / : OR #.
if delimiter char in $PWD, they will break the expression
the good way is replace(escape) the special character in $PWD.
二. good way: escape delimiter
for example:
try to replace URL as $url (has : / in content)
x.com:80/aa/bb/aa.js
in string $tmp
URL
A. use / as delimiter
escape / as \/ in var (before use in sed expression)
## step 1: try escape
echo ${url//\//\\/}
x.com:80\/aa\/bb\/aa.js #escape fine
echo ${url//\//\/}
x.com:80/aa/bb/aa.js #escape not success
echo "${url//\//\/}"
x.com:80\/aa\/bb\/aa.js #escape fine, notice `"`
## step 2: do sed
echo $tmp | sed "s/URL/${url//\//\\/}/"
URL
echo $tmp | sed "s/URL/${url//\//\/}/"
URL
OR
B. use : as delimiter (more readable than /)
escape : as \: in var (before use in sed expression)
## step 1: try escape
echo ${url//:/\:}
x.com:80/aa/bb/aa.js #escape not success
echo "${url//:/\:}"
x.com\:80/aa/bb/aa.js #escape fine, notice `"`
## step 2: do sed
echo $tmp | sed "s:URL:${url//:/\:}:g"
x.com:80/aa/bb/aa.js
With your question edit, I see your problem. Let's say the current directory is /home/yourname ... in this case, your command below:
sed 's/xxx/'$PWD'/'
will be expanded to
sed `s/xxx//home/yourname//
which is not valid. You need to put a \ character in front of each / in your $PWD if you want to do this.
Actually, the simplest thing (in GNU sed, at least) is to use a different separator for the sed substitution (s) command. So, instead of s/pattern/'$mypath'/ being expanded to s/pattern//my/path/, which will of course confuse the s command, use s!pattern!'$mypath'!, which will be expanded to s!pattern!/my/path!. I’ve used the bang (!) character (or use anything you like) which avoids the usual, but-by-no-means-your-only-choice forward slash as the separator.
Dealing with VARIABLES within sed
[root#gislab00207 ldom]# echo domainname: None > /tmp/1.txt
[root#gislab00207 ldom]# cat /tmp/1.txt
domainname: None
[root#gislab00207 ldom]# echo ${DOMAIN_NAME}
dcsw-79-98vm.us.oracle.com
[root#gislab00207 ldom]# cat /tmp/1.txt | sed -e 's/domainname: None/domainname: ${DOMAIN_NAME}/g'
--- Below is the result -- very funny.
domainname: ${DOMAIN_NAME}
--- You need to single quote your variable like this ...
[root#gislab00207 ldom]# cat /tmp/1.txt | sed -e 's/domainname: None/domainname: '${DOMAIN_NAME}'/g'
--- The right result is below
domainname: dcsw-79-98vm.us.oracle.com
VAR=8675309
echo "abcde:jhdfj$jhbsfiy/.hghi$jh:12345:dgve::" |\
sed 's/:[0-9]*:/:'$VAR':/1'
where VAR contains what you want to replace the field with
I had similar problem, I had a list and I have to build a SQL script based on template (that contained #INPUT# as element to replace):
for i in LIST
do
awk "sub(/\#INPUT\#/,\"${i}\");" template.sql >> output
done
If your replacement string may contain other sed control characters, then a two-step substitution (first escaping the replacement string) may be what you want:
PWD='/a\1&b$_' # these are problematic for sed
PWD_ESC=$(printf '%s\n' "$PWD" | sed -e 's/[\/&]/\\&/g')
echo 'xxx' | sed "s/xxx/$PWD_ESC/" # now this works as expected
for me to replace some text against the value of an environment variable in a file with sed works only with quota as the following:
sed -i 's/original_value/'"$MY_ENVIRNONMENT_VARIABLE"'/g' myfile.txt
BUT when the value of MY_ENVIRONMENT_VARIABLE contains a URL (ie https://andreas.gr) then the above was not working.
THEN use different delimiter:
sed -i "s|original_value|$MY_ENVIRNONMENT_VARIABLE|g" myfile.txt
Cannot seem to find an answer to this one online...
I have a string variable (externally sourced) with new lines "\n" encoded as strings.
I want to replace those strings with actual new line carriage returns. The code below can achieve this...
echo $EXT_DESCR | sed 's/\\n/\n/g'
But when I try to store the result of this into it's own variable, it converts them back to strings
NEW_DESCR=`echo $EXT_DESCR | sed 's/\\n/\n/g'`
How can this be achieved, or what I'm I doing wrong?
Here's my code I've been testing to try get the right results
EXT_DESCR="This is a text\nWith a new line"
echo $EXT_DESCR | sed 's/\\n/\n/g'
NEW_DESCR=`echo $EXT_DESCR | sed 's/\\n/\n/g'`
echo ""
echo "$NEW_DESCR"
No need for sed, using parameter expansion:
$ foo='1\n2\n3'; echo "${foo//'\n'/$'\n'}"
1
2
3
With bash 4.4 or newer, you can use the E operator in ${parameter#operator}:
$ foo='1\n2\n3'; echo "${foo#E}"
1
2
3
Other answers contain alternative solutions. (I especially like the parameter expansion one.)
Here's what's wrong with your attempt:
In
echo $EXT_DESCR | sed 's/\\n/\n/g'
the sed command is in single quotes, so sed gets s/\\n/\n/g as is.
In
NEW_DESCR=`echo $EXT_DESCR | sed 's/\\n/\n/g'`
the whole command is in backticks, so a round of backslash processing is applied. That leads to sed getting the code s/\n/\n/g, which does nothing.
A possible fix for this code:
NEW_DESCR=`echo $EXT_DESCR | sed 's/\\\\n/\\n/g'`
By doubling up the backslashes, we end up with the right command in sed.
Or (easier):
NEW_DESCR=$(echo $EXT_DESCR | sed 's/\\n/\n/g')
Instead of backticks use $( ), which has less esoteric escaping rules.
Note: Don't use ALL_UPPERCASE for your shell variables. UPPERCASE is (informally) reserved for system variables such as HOME and special built-in variables such as IFS or RANDOM.
Depending on what exactly you need it for:
echo -e $EXT_DESCR
might be all you need.
From echo man page:
-e
enable interpretation of backslash escapes
This printf would do the job by interpreting all escaped constructs:
printf -v NEW_DESCR "%b" "$EXT_DESCR"
-v option will store output in a variable so no need to use command substitution here.
Problem with your approach is use of old back-ticks. You could do:
NEW_DESCR=$(echo "$EXT_DESCR" | sed 's/\\n/\n/g')
Assuming you're using gnu sed as BSD sed won't work with this approach.
File.txt
/aaa/bbb/ccc/ddd
/aaa/bbb/ccc/mmm
/aaa/eee/ccc/ddd
if my $(pwd) is /aaa/bbb/ccc
the it should delete only first two
I have tried like sed /^$(pwd)/d but not worked
The problem here is that you are using $(pwd), which tries to execute a command pwd. This result contains slashes, so that the final command is something like:
sed /^/aaa/bbb/ccc/d
Which sed cannot handle and returns an error:
sed: -e expression #1, char 4: extra characters after command
You should instead use another delimiter. For example, _:
sed "\_${PWD}_d"
As 123 comments below, you need to escape the first delimiter if it is not a substitution. I also enclose the var within ${ } to prevent the variable to be considered PWD_ instead of PWD.
You can use awk for a nicer approach:
$ awk -v patt="$PWD" '!($0 ~ patt)' file
/aaa/eee/ccc/ddd
Note $PWD is the same as executing pwd.
grep can also do the job:
grep -v "$(pwd)" file
Just to precise the answer of fedorqui...
In your question there is another problem because you variable $pwd contain special sed symbols (/).
So the sed will not be glad...
Some solution for example could be find here : Replace a string in shell script using a variable
So you could use additional variable to correct this problem.
This work perfectly for your example (I just replace echo $(pwd) by 'echo /aaa/bbb/ccc').
pwd_bis=$( echo $(pwd) | sed 's/[\/]/\\\0/g' )
sed "/^${pwd_bis}/d" File.txt
Okay, I am a newbie to Unix scripting. I was given the task to find a temporary work around for this:
cat /directory/filename1.xml |sed -e "s/ABCXYZ/${c}/g" > /directory/filename2.xml
$c is a variable from a sqlplus count query. I totally understand how this sed command is working. But here is where I am stuck. I am storing the count associated with the variable in another file called filename3 as count[$c] where $c is replaced with a number. So my question is how can I update this sed command to substitute ABCXYZ with the count from file3?
>>>>>>>>>>>>>>>>>>>>>>>>>>>>
UPDATE: In case anyone has a similar issue I got mine to work using:
rm /directory/folder/variablefilename.dat
echo $c >> /directory/folder/variablefilename.dat
d=$(grep [0-9] /directory/folder/variablefilename.dat)
sed -3 "s/ABC123/${d}/g" /directory/folder/inputfile.xml >> /directory/folder/outputfile.xml
thank you to Kaz for pointing me in the right direction
Store the count in filename3 using the syntax c=number. Then you can source the file as a shell script:
. /filename3 # get c variable
sed -e "s/ABCXYZ/${c}/g" /directory/filename1.xml > /directory/filename2.xml
If you can't change the format of filename3, you can write a shell function which scrapes the number out of that file and sets the c variable. Or you can scrape the number out with an external program like grep, and then interpolate its output into a variable assignment using command substitution: $(command arg ...) syntax.
Suppose we can rely on file3 to contain exactly one line of the form count[42]. Then we can just extract the digits with grep -o:
c=$(grep -E -o '[0-9]+' filename3)
sed -e "s/ABCXYZ/$c/g" /directory/filename1.xml > /directory/filename2.xml
The c variable can be eliminated, of course; you can stick the $(grep ...) into the sed command line in place of $c.
A file which contains numerous instances of syntax like count[42] for various variables could be transformed into a set of shell variable assignments using sed, and then sourced into the current shell to make those assignments happen:
$ sed -n -e 's/^\([A-Za-z_][A-Za-z0-9_]\+\)\[\(.*\)\]/\1=\2/p' filename3 > vars.sh
$ . ./vars.sh
you can use sed like this
sed -r "s/ABCXYZ/$(sed -nr 's/.*count[[]([0-9])+[]].*/\1/p' path_to_file)/g" path_to_file
the expression is double quoted which allow the shell to execute below and find the number in count[$c] in the file and use it as a substitute
$(sed -nr 's/.*count[[]([0-9])+[]].*/\1/p' path_to_file)
I am trying to remove substring out of variable using sed like this:
PRINT_THIS="`echo "$fullpath" | sed 's/${rootpath}//' -`"
where
fullpath="/media/some path/dir/helloworld/src"
rootpath=/media/some path/dir
I want to echo just rest of the fullpath like this (i am using this on whole bunch of directories, so I need to store it in variables and do it automatically
echo "helloworld/src"
using variable it would be
echo "Directory: $PRINT_THIS"
Problem is, I can not get sed to remove the substring, what I am I doing wrong? Thanks
You don't need sed for that, bash alone is enough:
$ fullpath="/media/some path/dir/helloworld/src"
$ rootpath="/media/some path/dir"
$ echo ${fullpath#${rootpath}}
/helloworld/src
$ echo ${fullpath#${rootpath}/}
helloworld/src
$ rootpath=unrelated
$ echo ${fullpath#${rootpath}/}
/media/some path/dir/helloworld/src
Check out the String manipulation documentation.
To use variables in sed, you must use it like this :
sed "s#$variable##g" FILE
two things :
I use double quotes (shell don't expand variables in single quotes)
I use another separator that doesn't conflict with the slashes in your paths
Ex:
$ rootpath="/media/some path/dir"
$ fullpath="/media/some path/dir/helloworld/src"
$ echo "$fullpath"
/media/some path/dir/helloworld/src
$ echo "$fullpath" | sed "s#$rootpath##"
/helloworld/src