mjhjmtu

We want to add the following properties:

-XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M

in the two first lines that contain the word - HBASE_MASTER_OPTS

Example before change:

more ams-hbase-env-template.txt

export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSInitiatingOccupancyOnly" 
export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=71 -XX:+UseCMSInitiatingOccupancyOnly"
export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=72 -XX:+UseCMSInitiatingOccupancyOnly"
export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=73 -XX:+UseCMSInitiatingOccupancyOnly"

Example after change (expected results):

export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=70 -XX:+UseCMSInitiatingOccupancyOnly -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M" 
export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=71 -XX:+UseCMSInitiatingOccupancyOnly -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M"
export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=72 -XX:+UseCMSInitiatingOccupancyOnly"
export HBASE_MASTER_OPTS=" -XX:CMSInitiatingOccupancyFraction=73 -XX:+UseCMSInitiatingOccupancyOnly"

What I did until now is that:

sed -i '/HBASE_MASTER_OPTS/ s/$/-XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M/' ams-hbase-env-template.txt

But this isn't right because:

1. We want the properties before the end of double quote.




2. Properties must be only on the first two lines that variable is HBASE_MASTER_OPTS.




3. In case properties are already in line, then it will not append again on any next time!

Extending on Steve's answer:

awk '/HBASE_MASTER_OPTS/&&/ -XX:[+]UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M/x++;print;next/HBASE_MASTER_OPTS/&&x<2gsub(/"$/," -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M"");x++1' ams-hbase-env-template.txt

Update: Here's a more maintenance friendly version, where every string only occurs once.

awk 'BEGINp="-XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M"m=0/HBASE_MASTER_OPTS/m=1;++xm&&index($0,p)print;nextm&&x<=2gsub(/"$/," " p """)1' ams-hbase-env-template.txt

And some explanation:

• In the first version in the pattern matching, [+] is used for the literal + character, because otherwise + would be interpreted as special character.

The remaining points are about the second version:

• In the BEGIN clause, the properties string p is defined. All the following clauses apply to the lines of the input.


• 
  m=0: This clause has no condition, which means it applies to every line, such that for each line first m (for match) will be set to zero.


• 
  /HBASE_MASTER_OPTS/m=1;++x: If a line matches the HBASE_MASTER_OPTS string, m is set and our line counter is incremented.


• 
  m&&index($0,p)print;next: this clause checks if, in addition to a match indicated by m, also the properties string is contained in the input line. In such a case index will return an non-zero value. If so, we print the line as it is (not adding the properties again) and with next skip the remaining clauses and start processing the next line. Note that the following clauses were originally provided by Steve and only adapted by me:


• 
  m&&x<=2gsub(/"$/," " p """): if we reach this point and we have a matching line and our counter has not exceeded 2, we modify $0 (the input line) by prepending the terminal " with a blank and our properties string. Apart from that, no output is produced, which will be done by the next clause.


• 
  1: This is a condition (always true) without an action, which means the action defaults to printing the input line.

How about this awk solution. Creates the desired output in the question.

awk '/HBASE_MASTER_OPTS/&&x<2gsub(/"$/," -XX:+UseGCLogFileRotation -XX:NumberOfGCLogFiles=5 -XX:GCLogFileSize=2M"");x++1' ams-hbase-env-template.txt

Try it online!