Environment variable substitution in sed

Question

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

User · Answer

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

User · Answer

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  gt  gt  output done

User · Answer

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

User · Answer

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

User · Answer

Another easy alternative   Since  PWD will usually contain a slash    use   instead of   for the sed statement   sed -e  s xxx  PWD

User · Answer

VAR 8675309 echo  quot abcde jhdfj jhbsfiy  hghi jh 12345 dgve   quot     sed  s   0-9       VAR   1    where VAR contains what you want to replace the field with

User · Answer

Dealing with VARIABLES within sed   root gislab00207 ldom   echo domainname  None  gt   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

User · Answer

bad way  change delimiter sed  s xxx   quot  PWD quot     sed  s xxx   quot  PWD quot     sed  s xxx   quot  PWD quot      maybe those not the final answer  you can not known what character will occur in  PWD      OR    the good way is replace escape  the special character in  PWD     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  lt a href  quot URL quot  gt URL lt  a gt   A  use   as delimiter escape   as    in var  before use in sed expression  echo   url          x com 80  aa  bb  aa js    escape fine  echo   url         x com 80 aa bb aa js       escape not success  echo  quot   url         quot  x com 80  aa  bb  aa js    escape fine  notice   quot    echo  tmp   sed  quot s URL   url           quot   lt a href  quot x com 80 aa bb aa js quot  gt URL lt  a gt   echo  tmp   sed  quot s URL   url          quot   lt a href  quot x com 80 aa bb aa js quot  gt URL lt  a gt   OR B  use   as delimiter  more readable than    escape   as    in var  before use in sed expression  echo   url        x com 80 aa bb aa js      escape not success  echo  quot   url        quot  x com  80 aa bb aa js     escape fine  notice   quot    echo  tmp   sed  quot s URL   url        g quot   lt a href  quot x com 80 aa bb aa js quot  gt x com 80 aa bb aa js lt  a gt

User · Answer

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

User · Answer

You can use other characters besides     in substitution   sed  s  1  2 g  -i FILE

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