3

File:

TABLE1

1234 
9555    
87676  
2344

Expected output:

Description of the following table:
TABLE1

1234
9555
87676
2344
Thor
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Nainita
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  • @don_crissti: Because this question includes an `awk` tag, I would argue that it is closely related but not a duplicate. – Thor May 06 '16 at 11:43
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    @Thor it's the same problem, solved in the same way with the same set of tools. that's far more significant than the tags. unless the question says something like "i don't have foo installed" or "i am required to write this in bar" then an answerer is at liberty to ignore the tags and write an answer using whatever tool they think is best for the job at hand....or just to provide an alternate method using a different tool. – cas May 06 '16 at 12:04

4 Answers4

9

Actually echo and cat are enough to do what you want :

echo "Description of the following table:" | cat - file

The - argument tells cat to read from stdin.

Aaron
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  • but how to stop output of the this operation to terminal ? – Mysterious Jack Feb 20 '22 at 13:05
  • @MudassirHussain ctrl-c should stop the output of the `cat` operation. It sometimes looks like it doesn't if `cat` has finished outputting its text but your console is still busy displaying (which can take much more time) – Aaron Feb 21 '22 at 17:42
  • Not bad, but this doesn't exactly answer OPs question, which seems to want to add "in place". In other words, this does not work, any idea? `echo "Description of the following table:" | cat - file > file`. EDIT: this does the trick! `echo "Description of the following table:" | cat - file | tee file` – Kiteloopdesign Aug 23 '22 at 09:33
8

With sed:

$ sed -e '1i\
Description of the following table:
' <file
Description of the following table:
TABLE1

1234
9555
87676
2344
cuonglm
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6
printf "%s\n" 1 i "Description of the following table:" . w | ed filename

The printf outputs ed commands (one per line) which are then piped into ed filename.

ed edits the file as instructed:

1                                        # go to line 1
i                                        # enter insert mode
Description of the following table:      # text to insert
.                                        # end insert mode
w                                        # write file to disk

BTW, ed performs a real in-place edit, not write-to-temp-file-and-move like sed and most other text editing tools. The edited file keeps the same inode in the filesystem.

cas
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  • also BTW, `ed` can do pretty much everything that `sed` can. `sed` is the stream-oriented clone of `ed`, after all. GNU `ed`'s man page is almost useless, but full documentation is available with `info ed` (or bettter yet, `pinfo ed`). – cas May 06 '16 at 11:43
  • but this prints output to terminal. how to avoid that? – Mysterious Jack Feb 20 '22 at 12:42
  • @MudassirHussain read the man page. it documents the `-s` (`--silent`, `--quiet`) option. and/or just redirect `ed`'s output to /dev/null as you would with any other program the outputs stuff you don't want to see. – cas Feb 21 '22 at 00:52
2

The awk option would be :

gawk '
      BEGIN{print "Description of the following table:"}
      {print $0}' file > temp && mv temp file

A bit more work than sed here because sed has got an in-place edit option -i by which you could directly write to file.

sjsam
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