CODEWITHSUNDEEP
shellawk
User
User

Reputation: 411

line traversal in awk

I am doing a file traversal in awk. An example of this is

Dat time range column session - 1
time name place session animal - 2 
hi bye name things - 3

In both of these . I need to traverse line by line and in I need to traverse word by word in the line that contains session .

Thus in this case I need to reach line 1 and 2 as it contains the word session and not line 3 as it doesn't contain that field(In the sense I can skip this). From there I need to traverse word by word to reach the session field .

I know $0 can represent the whole line. But my question is how to traverse word by word after reaching the line.

Could you please help me regarding this. Thank you.

Upvotes: 0

Views: 398

Answers (2)

Shahbaz
Shahbaz

Reputation: 47503

You can use a for loop, filtering only on the lines that contain "session":

awk '/session/{ for (i = 1; i <= NF; i++) { \
                  if ($i == "session") \
                    do_whatever_here \
                } \
              }'

You can read more on these instructions here: for, string comparison and if.

Upvotes: 1

Levon
Levon

Reputation: 143047

You can loop through the current line $0 with this construct:

for(i = 1; i <= NF; i++) print $i

this makes use of the predefined awk variable NF which stands for the number of fields on the current line ($0).

You can examine the value of $i as it iterates through the line and based on that determine what to do with the value. E.g, print it, skip it, etc. if ($i == "session") ...

Update:

You can also use the match() function to determine if the current line you are processing contains the "session" string without iterating through the line. E.g.,

where = match($0, "session")
if (where > 0)
   print "Found session in this line";
else
   print "session not found in this line";

Note that match() takes a regular expression as the 2nd parameter, so your matches can be quite sophisticated. See this page for more information about this function and other awk string functions.

Upvotes: 1

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