CODEWITHSUNDEEP
shellsed
xxks-kkk
xxks-kkk

Reputation: 2608

Insert line if pattern doesn't match otherwise modify the line with the pattern

Suppose I want to modify a file foo.ini with the following sed:

bar="hello"

sed -i "                                                                                                                                                             
# if there is NZ variable in db2dj.ini, we simply set it to the proper value                                                                           
s/NZ=*/NZ=$bar/

# if there is no NZ variable, we add NZ_ODBC_INI_PATH variable and set the proper value to it                                                          
T add


:add
$ i\NZ_ODBC_INI_PATH=$db2dj_nz_odbc_ini_path

" foo.ini

Suppose foo.ini is empty at first. Then I run the sed above and I got:

NZ=hello

This is fine. However, if I run the same sed command again, foo.ini will become:

NZ=hellohello
NZ=hello

My ideal for sed command is that:

  1. if there is no NZ variable, then it add NZ=hello to it

  2. if there is already NZ variable with form like NZ=hi, it will change it to NZ=hello

  3. Only when NZ=hello should appear in foo.ini

How do I modify the above sed command to achieve this task? I believe my sed command works fine with (1) but not with (2) (3)

Many thanks!

Upvotes: 0

Views: 33

Answers (1)

riteshtch
riteshtch

Reputation: 8769

A simple grep check is sufficient: 

grep -q '\bNZ=\b' foo.ini > /dev/null 2>&1 && sed -i 's/NZ=.*$/NZ=hello/' foo.ini || echo "NZ=hello" >> foo.ini

The above statement will insert if no variable present. Also it handles substitution if already present with a different/same value.

$ cat foo.ini
cat: foo.ini: No such file or directory
$ grep -q '\bNZ=\b' foo.ini > /dev/null 2>&1 && sed -i 's/NZ=.*$/NZ=hello/' foo.ini || echo "NZ=hello" >> foo.ini
$ cat foo.ini 
NZ=hello
$ grep -q '\bNZ=\b' foo.ini > /dev/null 2>&1 && sed -i 's/NZ=.*$/NZ=hello/' foo.ini || echo "NZ=hello" >> foo.ini
$ cat foo.ini 
NZ=hello
$ vim foo.ini 
$ cat foo.ini 
NZ=hi
$ grep -q '\bNZ=\b' foo.ini > /dev/null 2>&1 && sed -i 's/NZ=.*$/NZ=hello/' foo.ini || echo "NZ=hello" >> foo.ini
$ cat foo.ini 
NZ=hello

Upvotes: 2

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