Extract line beginning with a specific pattern in sed

command-line text-processing sed text regex

8,330

Solution 1

egrep can get multiple lines from a file. Using a pipe | as a separator you can pull as many different criteria as you want. egrep is the equivalent of grep -E. egrep is a script found in the /bin folder with the contents pointing to exec grep -E "$@".

Example:

egrep "IDno=|Type=Student" inputfile

grep -E "IDno=|Type=Student" inputfile

Should output:

IDno="1"
Type=Student
IDno="2"

Hope this helps!

Solution 2

With sed, to print specific lines, it's easier to use the -n option and the p command:

sed -rn '/IDno=|Type=Student/p'

Or:

sed -n -e '/IDno=/p' -e '/Type=Student/p'

The -n option suppresses output unless explicitly print. The p command, of course, prints matching lines.

Solution 3

awk:

Setting the field separator as =, and printing the records that contain Type=Student as the whole record or IDno as the first field:
```
awk -F= '$1=="IDno" || $0=="Type=Student"'
```
perl:

Printing the lines that start with IDno followed by =, or start with Type, followed by a = and end in Student:
```
perl -ne 'print if /^(IDno=|Type=Student$)/'
```

Example:

% cat file.txt                                  
IDno="1"
Name=Jack
Type=Student
IDno="2"
Name=Jill
Type=Teacher

% awk -F= '$1=="IDno" || $0=="Type=Student"' file.txt
IDno="1"
Type=Student
IDno="2"

% perl -ne 'print if /^(IDno=|Type=Student$)/' file.txt
IDno="1"
Type=Student
IDno="2"

8,330

Admin

Updated on September 18, 2022

Comments

Admin over 1 year
My input file is like this:
```
IDno="1"
Name=Jack
Type=Student
IDno="2"
Name=Jill
Type=Teacher
```
I am using sed to extract all the IDno and the type only when type is student.
```
sed -e '/IDno=/b' -e '/Type=Student/b' d
```
This gets me all lines with type student but not the IDnos.

I want to get
```
IDno="1"
Type=Student
IDno="2"
```
but I am getting
```
Type=Student
```
What am I doing wrong?
- Terrance about 7 years
  
  Wouldn't egrep be easier? egrep -e "IDno=|Type=Student" inputfile
- steeldriver about 7 years
  
  Did you mean to write -e d (not just d)? otherwise the command is malformed I think. Regardless, it would be more idiomatic to invert the logic using ! rather than by branching past the d i.e. sed '/IDno=\|Type=Student/!d'
heemayl about 7 years

egrep is deprecated in favor of grep -E, it's time to get rid of the cliché...
Xen2050 about 7 years

This return every single "IDno=" line, regardless of whether or not the "Type=Student" two lines down. That appeared to be part of the original question, to only return IDno's for "Student"s, but the OP seems to like this, so...?
muru about 7 years

The example output clarifies that.
Xen2050 about 7 years

@muru Thanks, I just noticed that too, seems to be a mistake IMO either in the description or example output. Actually found a mistake in my answer too, pasting the Name after ID... Maybe someone will find this answer useful anyway (especially after/if I fix it), I'm still learning from it\
Xen2050 about 7 years

That is good, pipeing it back to grep again to only return the ID & Type lines gets rid of the Name too (and the -- separator line), like adding |grep "IDno=\|Type="
muru about 7 years

read it this way "(all the IDno) and (the type only when type is student)"
Terrance about 7 years

@heemayl Good point! =) Old habits die hard I guess. Maybe one day they'll remove the script, but from my understanding is that it is left in there for older applications that rely on them to not be modified.