Move a line to top of the file

Shell Programming and Scripting
1

Hi,
I have a following file and it has only one occurrence of line that says "Output view:". It could be in middle somewhere ( i don't know the exact location ). I want to move it as the first line of the file.

Input

AAA
BBBB
CCCC
Output view:
XXXX
YYYY
ZZZZ

Output should be:

Output view:
AAA
BBBB
CCCC
XXXX
YYYY
ZZZZ
2 
sed '/Output view:/d;1i\Output view:' file

Emanuele

3

Lazy (but easy to read) solution...

grep "Output view:" input >output
grep -v "Output view:" input >>output

But no doubt it must be some more elegant solution ...

@Alister :
Any "ed" suggestion ? :wink:

4

Hi,
Another sed solution (also work with regular expression):

 sed -n '1,/Output view:/{/Output view:/{G;s/\n//p;b;};H;b};p' file

Regards.

5

Thanks guys!

6

Yet another way with the trusty ole ex...

ex -s +'/^Output view:/m0 | x' file
1 Like
7

Two more:

awk '/Output view:/{f=1; $0=$0 p; p=x} !f{p=p RS $0} f' file

or perhaps simply

awk 'NR==1{print s} $0!~s' s="Output view:" file
1 Like
8 
#!/bin/ksh
infile="Input"
outfile="Output"
ed -s "$infile" <<-EOF
        /Output view:/m0
        w $outfile
        q
EOF

This was tested using the Korn shell, but will work with any shell that accepts basic Bourne shell syntax.

1 Like
9

Hi,

May be this code can help too.

$ awk '
BEGIN{
print "Output view:"
} NR==4 || /Output/ {next} {print $1}' file_name

Output will be as follows.

Output view:
AAA
BBBB
CCCC
XXXX
YYYY
ZZZZ

Thanks,
R. Singh

10

Nice.

I found this about the use of + :

ex: Rationale - options

This seems to work too:

ex -sc '/^Output view:/m0 | x' file
1 Like
11

One more lengthy way

may try

$ awk 'BEGIN{while(1){getline;if(/Output/){printf $0;break}x=x RS $0}print x}1'  file

OR

$ awk '{if(/Output/)printf $0;else x=x RS $0}END{print x}' file

Resulting

Output view:
AAA
BBBB
CCCC
XXXX
YYYY
ZZZZ
2 Likes
12 
sed -e '/^Output view:/{G;p;}' -e '1{h;d;}' -e '2,/^Output view:/{H;d;}' file

maybe better readable as

sed '
/^Output view:/{G;p;}
1{h;d;}
2,/^Output view:/{H;d;}
' file

But sed is hacking; the string must be mentioned twice. awk is better:

awk 'p; /^Output view:/ {print; print s; p=1} !p {s=s sep $0; sep=RS}' file
13

sir,

code

awk '/Output view:/{f=1; $0=$0 p; p=x} !f{p=p RS $0} f' file

works fine. But can you explain me step by step by step how it works.

14

Reformatting Scrutinizer's code and adding comments:

awk '           # invoke awk program and start script to be run by awk
/Output view:/ {# When an input line contains the string "Output view:"...
        f=1             # set f (found) to 1,
        $0=$0 p         # append the contents of p to the end of the
                        # current input line, and 
        p=x             # set p to the contents of x (an empty string) 
}       
!f {            # If f is 0...
        p=p RS $0       # append the record separator (default value is
                        # the newline character) and the current input
                        # line to p
}       
f               $ If f is not 0, print the current input line.
' file          # End awk script and specify the name of the input file.
4 Likes