Shell Programming and Scripting

Hi,

I'm new to sed and I don't really need to know much about it quite yet. However, in the code I'm reading I keep seeing the following line in a bash file (They are using it to create file names). Could someone please explain to me what it means? I'm familiar with regular expressions and it looks like they are doing a search and replace, but I'm not sure. I know the .* is grab everything, but a space. I think the -e option means that multiple commands may be specified......advice!

Code:

PLUGIN_OUT_SFF_NAME = `echo ${TSP_FILEPATH_SFF} | sed -e 's_.*/__g'`;

Thanks

.* means any character (and that includes space) any number of times.

Your command is removing the longest string ending with /.

E.g.,

Code:

$ echo "HI THERE"|sed -e 's_.*/__g'
HI THERE

$ echo "HI THERE/"|sed -e 's_.*/__g'


$ echo "HI THERE/YOU THERE"|sed -e 's_.*/__g'
YOU THERE

$ echo "HI THERE/YOU THERE/THEY THERE"|sed -e 's_.*/__g'
THEY THERE

The -e option is used to specify an expression/script to sed. It is redundant in your case and is required only if you have multiple separate scripts.

Thanks!

Would you mind answering one more question? This is another one I'm seeing a lot of in the bash, but this time it's with awk.

Code:

BARCODE_ID=`echo ${BARCODE_LINE} | awk 'BEGIN{FS=","}{print $2}'`;

All know is that the barcode line that was grabbed out of a text file is being cut up. (I'm supposedly extracting just the BARCODE_ID from the BARCODE_LINE)

That's printing the second field in the variable value where the field-separator is a comma.

E.g., if BARCODE_LINE contains "FIELD 1,FIELD 2,FIELD 3,FIELD 4", after this assignment BARCODE_ID would have "FIELD 2".

Perfect!

These scripts you're leaning from don't look like very good scripts.

Running awk, sed, etc to process single lines is incredibly wasteful.

Well, I didn't write them. They are part of the plugin scripts for our ion torrent server. Why are one liners bad?