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Full Discussion: Question about a awk command
Top Forums Shell Programming and Scripting Question about a awk command Post 302873885 by jeffwang66 on Wednesday 13th of November 2013 11:36:00 AM
Old 11-13-2013
Question about a awk command

Hi,

I am studying an awk command:
Code:
awk '{ sub(/\/\/.*/, "", $NF); print }' input.txt

The input.txt is:
Code:
char*s1="//hello"; //comment
//delete
/* hello //*/

The output is :
Code:
char*s1="//hello";

/* hello

My question is why the contents ("//hello") is not deleted? And what does $NF mean?

Thanks

Last edited by Scott; 11-13-2013 at 12:40 PM.. Reason: Code tags
 

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X2SYS_MERGE(1gmt)					       Generic Mapping Tools						 X2SYS_MERGE(1gmt)

NAME
x2sys_merge - Merge an updated COEs tables SYNOPSIS
x2sys_merge -Amain_COElist.d -Mnew_COElist.d DESCRIPTION
x2sys_merge will read two crossovers data base and output the contents of the main one updated with the COEs in the second one. The second file should only contain updated COEs relatively to the first one. That is, it MUST NOT contain any new two tracks intersections (This point is NOT checked in the code). This program is useful when, for any good reason like file editing NAV correction or whatever, one had to recompute only the COEs between the edited files and the rest of the database. -A Specify the file main_COElist.d with the main crossover error data base. -M Specify the file new_COElist.d with the newly computed crossover error data base. OPTIONS
No space between the option flag and the associated arguments. EXAMPLES To update the main COE_data.txt with the new COEs estimations saved in the smaller COE_fresh.txt, try x2sys_merge -ACOE_data.txt -MCOE_fresh.txt > COE_updated.txt SEE ALSO
x2sys_binlist(1), x2sys_cross(1), x2sys_datalist(1), x2sys_get(1), x2sys_init(1), x2sys_list(1), x2sys_put(1), x2sys_report(1) GMT 4.5.7 15 Jul 2011 X2SYS_MERGE(1gmt)
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