Non printing option in sed is behaving oddly


 
Thread Tools Search this Thread
Top Forums UNIX for Beginners Questions & Answers Non printing option in sed is behaving oddly
# 1  
Old 07-07-2019
Non printing option in sed is behaving oddly

Hi I'm having a problem with a sed command that I thought I was using correctly but apparently that's not the case.

I was hoping someone here could point out what it is I am doing wrong?
I am using the print, no print option for a matched pattern in sed. Everything seemed to be working fine except I noticed that some lines that were matching my pattern are missing from my output.

After doing a little digging I found that after the command matched a pattern, if the next line also matched the pattern it would fail to output the second matched pattern line.
Can any one see why its behaving this way?
Below is the command I am using
Code:
sed -n -e '/\<PreviousJobNum\>[A-Z]*[0-9][0-9]*[A-Z]*\<\/PreviousJobNum\>/{p;n;}' /MyInputFile > /MyOutPutFile

The file I am reading in is MyInputFile, the content of which is
Code:
<PreviousJobNum>93296</PreviousJobNum>
<PreviousJobNum>95879D</PreviousJobNum>

When I run the above command my output in MyOutPutFile is
Code:
<PreviousJobNum>93296</PreviousJobNum>

If I change the data slightly in the original MyInputFile to have line between the two matched pattern lines, like below,
Code:
<PreviousJobNum>93296</PreviousJobNum>


<PreviousJobNum>95879D</PreviousJobNum>

Then my output Picks up both matched pattern lines in the MyOutPutFile as below.
Code:
<PreviousJobNum>93296</PreviousJobNum>
<PreviousJobNum>95879D</PreviousJobNum>

I suppose I could double space my input file to get around this but I think it would be better to understand why its behaving this way?
if anyone was able to offer some assistance with this I would be very grateful.
Thank you very much
Paul

Last edited by Scrutinizer; 07-07-2019 at 10:24 PM.. Reason: Removed hyperlink
# 2  
Old 07-07-2019
The n command fetches the next input line. No sed code follows that does something on it, so it goes to the next cycle that - as usual - fetches the next input line, in this case the over-next line.

Note that the n command behaves different from the next instruction in awk and perl (that jumps to the end of the input loop). This is like the b command in sed (without a label).

If there is no further code then you can simply omit the n command.
This User Gave Thanks to MadeInGermany For This Post:
# 3  
Old 07-07-2019
Note that you can simplify your sed script using a "back reference" on top of other sed idiosyncrasies (cf man sed):


Code:
sed -rn  '\#<(PreviousJobNum>)[A-Z]*[0-9]+[A-Z]*</\1#p' file
<PreviousJobNum>93296</PreviousJobNum>
<PreviousJobNum>95879D</PreviousJobNum>

This User Gave Thanks to RudiC For This Post:
# 4  
Old 07-07-2019
Thank you for clearing that up Smilie
# 5  
Old 07-07-2019
To add, you can use the d command to go to the next cycle without further processing.
This User Gave Thanks to Scrutinizer For This Post:
# 6  
Old 07-08-2019
Thank you I will try using that as well! Smilie
Login or Register to Ask a Question

Previous Thread | Next Thread

10 More Discussions You Might Find Interesting

1. UNIX for Beginners Questions & Answers

Non printing option in sed is behaving oddly

Hi I'm having a problem with a sed command that I thought I was using correctly but apparently that's not the case. I was hoping someone here could point out what it is I am doing wrong? I am using the print, no print option for a matched pattern in sed. Everything seemed to be working fine... (2 Replies)
Discussion started by: harveyclayton
2 Replies

2. Shell Programming and Scripting

sed parser behaving strange on replacing multiple words in multiple files

I have 4000 files like $cat clus_grp_seq10_g.phy 18 1002 anig_OJJ65951_1 ATGGTTTCGCAGCGTGATAGAGAATTGTTTAGGGATGATATTCGCTCGCGAGGAACGAAGCTCAATGCTGCCGAGCGCGAGAGTCTGCTAAGGCCATATCTGCCAGATCCGTCTGACCTTCCACGCAGGCCACTTCAGCGGCGCAAGAAGGTTCCTCG aver_OOF92921_1 ... (1 Reply)
Discussion started by: sammy777888
1 Replies

3. Solaris

Remove oddly named file

I accidentally saved a txt file in vi with the name ":q!". no amount of regex tomfoolery I can think of will allow me to remove the file. anyone got any ideas? (4 Replies)
Discussion started by: os2mac
4 Replies

4. Shell Programming and Scripting

sed one Liner option -e

Hi, I have the following command.(Delete all trailing blank lines at the end of a file.) sed -e :a -e '/^\n*$/{$d;N;ba' -e '}' I don't understand the logic of this command and also I don't understand why -e is used. Can you please let me know the logic of this command and why three -e... (5 Replies)
Discussion started by: TomG
5 Replies

5. Shell Programming and Scripting

sed -n option

Hi i am facing problem with sed -n option could you please help me on this, i have a file test the contents of the file is width="75">10/0 4/12</td>^M><a href='courtorders/100412zr.pdf' target="_blank">Miscellaneous Order</a></td>^M width="75">10/01/12</td>^M><a href='courtorde... (8 Replies)
Discussion started by: ragilla
8 Replies

6. Shell Programming and Scripting

sed with -e option

sed "s/^/8,A1,$dat,id2_3,/g" -e sed "s/$/,,,,,,,,,,,/g" temporary wn m running this script m getting a error... plz help me with this.... O/p sed: -e expression #1, char 3: unterminated `s' command ---------- Post updated at 11:35 AM ---------- Previous update was at 11:33 AM... (7 Replies)
Discussion started by: nikhil jain
7 Replies

7. Shell Programming and Scripting

sed behaving oddly, repeats lines

Hi, all. Here's the problem: sed '/FOO/,/BAR/p' That should print anything between FOO and BAR, right? Well, let's say I have file.txt that contains just one line "how are you today?". Then I run something like the above and get: $ sed '/how/,/today/p' file.txt how are you... (9 Replies)
Discussion started by: pereyrax
9 Replies

8. Shell Programming and Scripting

sed 'b' option

Hi, What does the following command do on files? sed '1b; $d' To me it just deletes the last line of the file. If so what is the significance of sed's 'b' option? Thanks (1 Reply)
Discussion started by: royalibrahim
1 Replies

9. UNIX for Dummies Questions & Answers

sed -i option example

Can anyone give detailed and example for sed -i option. Where can we use this option?:) (3 Replies)
Discussion started by: gwgreen1
3 Replies

10. Shell Programming and Scripting

sed and cut behaving differently

I have attached a file with few records. First 2 characters of each record are binary characters. I can remove it by and it works fine. But is behaving differently and removing more than expected characters. Can someone help me in accomplishing it through sed? Thanks in advance. (13 Replies)
Discussion started by: amicon007
13 Replies
Login or Register to Ask a Question