In-place editing using sed on AIX

Question

Is there any undocumented flag in AIX's sed implementation that allows for in-place editing in the same way as with e.g. GNU sed? The manual shows no flag for this operation, which is one of the most useful ones in other sed implementations.

If you don't see it in the man page, you can be pretty sure it doesn't exist. Just use sed 's/a/b/' foo > bar && mv bar foo — terdon, Jan 30 '14 at 14:19
Just one thing to note regarding @terdon's suggestion: that may result a foo file with different owner/permissions than the original one. — manatwork, Jan 30 '14 at 15:03
@manatwork so will sed -i (at least on my Debian). It works by creating a temp file in the backgroud and renaming it to the original file's name so it will be owned by whoever ran the sed. — terdon, Jan 30 '14 at 15:06
@terdon, it was installed the last time I used AIX 15 years ago (but then again it might not have come pre-installed on those machines) and had the -i option (which is where GNU and FreeBSD sed got the inspiration from for their -i decades after perl). — Stéphane Chazelas, Jan 30 '14 at 15:10
@terdon, the GNU sed 4.2.2 I tried before my previous comment sets the ownership and permissions of the new file to match the old one. — manatwork, Jan 30 '14 at 15:30
@manatwork ok, very weird. The GNU sed 4.2.2 I tried here changes the ownership of my test file (permissions 777, in a directory with 777) to my user. — terdon, Jan 30 '14 at 15:37
@terdon, probably my test case was too simple. I processed a file owned by user manatwork as user root. So changing the ownership had no impediments. — manatwork, Jan 30 '14 at 15:43
@terdon - yes, perl is most likely present on modern AIX systems ( I used it on AIX 6 and 7) — MAQ, Mar 01 '16 at 17:58

score 4 · Answer 1 · edited Nov 20 '15 at 10:12

4

you can use perl to do it:

perl -p -i.bak -e 's/old/new/g' test.txt

It's going to create a .bak file.

Or without a .bak file :

perl -pi -e  's/old/new/g' test.txt

Or install sed-4.1.1 RPM from here.

edited Nov 20 '15 at 10:12

Kevdog777

3,224

answered Nov 20 '15 at 09:47

Jaoued Zahraoui

41

score 3 · Answer 2 · edited Mar 12 '19 at 07:12

3

This is not possible on AIX even with the sed tool installed.
You do need to use a temp file like suggested by terdon in comments to the question:

sed 's/a/b/' foo > bar && mv bar foo

You could also use ed which does inline editing.

edited Mar 12 '19 at 07:12

Kusalananda

333,661

answered Jan 30 '14 at 14:28

Kiwy

9,534

Why would it not be possible with GNU sed installed? – Stéphane Chazelas Jan 30 '14 at 14:42
well the GNU provided by AIX not the one you can compile see also ==> https://stackoverflow.com/questions/7232797/sed-on-aix-does-not-recognize-i-flag – Kiwy Jan 30 '14 at 14:43
2

-i was added in sed-3.95 (2002). IBM offers 3.0.2, 4.0.7 and 4.1.1 AFAICT. Unless you get the older one, you'll get -i. Also note that you can get packaged version of GNU sed for AIX from other sources. – Stéphane Chazelas Jan 30 '14 at 15:08
Well it means my admin system never updated since 2002 I guess. because even with AIX 6.1 I don't have the possibility to use that switch – Kiwy Jan 30 '14 at 15:17
@Kiwy, run away as fast as you possibly can. A system that hasn't been properly maintained for a dozen years... the mind boggles. – vonbrand Jan 30 '14 at 15:23
@vonbrand AIX 6.1 has been release in 2007 so I guess -i is not available since 2002 – Kiwy Jan 30 '14 at 15:27
@Kiwy you -i is from GNU sed which you don't have installed. – terdon Jan 30 '14 at 15:36
@Kiwy - there is also pre-build GNU sed package http://www.perzl.org/aix/index.php?n=Main.Sed – MAQ Mar 01 '16 at 18:00
@StéphaneChazelas on a fairly stock AIX7.1 machine I have access to, IBM's sed still does not support -i. I could not determine the sed version - it rolls up to the bos.rte.edit package. – Jeff Schaller Apr 20 '16 at 15:05
@JeffSchaller, yes nobody said AIX sed supported -i, just that you could get GNU sed for AIX. – Stéphane Chazelas Apr 20 '16 at 15:22
1

@StéphaneChazelas I was reading between the lines of your comment from 2 years ago: "-i was added in sed-3.95 (2002). IBM offers 3.0.2, 4.0.7 and 4.1.1 AFAICT" the implication that you saw recent versions of AIX offering sed's that supported -i. – Jeff Schaller Apr 20 '16 at 15:25

score 3 · Answer 3 · edited Dec 05 '22 at 21:57

3

To use a standard compliant sed, which does not have -i, to do in-place editing, in such a way that permissions, file ownerships and some other metadata are not modified and hard links and symlinks are not broken:

cp file file.tmp &&
  sed 'expression' file.tmp >file &&
  rm -f file.tmp

This creates a temporary copy of the file we want to edit, and then applies the sed command to this copy while redirecting the result to the original filename.

Redirecting to the original filename will truncate and rewrite that file, and since the file is not first deleted and recreated, it will retain most of its metadata.

edited Dec 05 '22 at 21:57

Stéphane Chazelas

544,893

answered Mar 11 '19 at 10:32

Kusalananda

333,661

1

fwiw, that's not what sed is doing. sed is redirecting the output to a temp file, copy through the permissions and finally rename the temp file to the original. That will change the file's inode and wipe some precious metadata but a) will not trash the file's content if the sed -i command was interrupted or failed b) will not trash the file's content if more that one sed -i was run on the same file at the same time. More details and ranting here. – Mar 12 '19 at 14:15
1

@mosvy All true. The way I have arranged the commands in my answer will ensure that the original contents (at least) is still available in the temporary file if the sed fails. – Kusalananda Mar 12 '19 at 14:40

score -1 · Answer 4 · edited Mar 01 '16 at 14:56

-1

Define a variable and use a subshell to execute sed and redirect to a file. Very important use " (double quote) to protect the variable $value:
```
value=$(sed 's/old/new/g' file) && echo "$value" > file
```

Or

Execute echo with a subshell you going to execute 'sed' and redirect to a file:
```
echo "$(sed 's/old/new/g' file)" > file
```

edited Mar 01 '16 at 14:56

techraf

5,941

answered Mar 01 '16 at 14:24

Edson

9

That is just a convoluted way of doing what the comment by @terdon does. Better yet, grab the GNU sed and install that. – vonbrand Mar 01 '16 at 14:53
option #2 will most likely truncate 'file' before reading from it -- be careful! – Jeff Schaller Mar 01 '16 at 14:55
@JeffSchaller : no, because the subshell should end before print opens its fd. – Mat M Jul 19 '18 at 12:53
Use print with ksh or you will lose the line feeds. – Mat M Jul 19 '18 at 12:54
@vonbrand : it avoids creating a temp file, and it is sometimes a requirement – Mat M Jul 19 '18 at 12:55

score -1 · Answer 5 · edited Dec 07 '22 at 07:49

Or use a here doc with ed -s. Sample short script - this hand copied, so may have a typo but the code is correct.

#!/bin/ksh
echo "test heredoc by adding def to a line with abc"
ed -s ./foo <<\END
1,$p /abc/s/$/def/p w
q
.
END
echo DONE

Test file foo:

This is the test file
qwerty
asdfg
AWEfgEDH
abc this line needs def at the end!!!
asfpgt

My sample output:

97
abc this line needs def at the end!!!def
100
DONE

In-place editing using sed on AIX

5 Answers5

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