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Full Discussion: Removing lines from a file being used by another process using SHELL script
Top Forums Shell Programming and Scripting Removing lines from a file being used by another process using SHELL script Post 302705521 by Ygor on Tuesday 25th of September 2012 04:39:42 AM
Old 09-25-2012
I would guess that it depends on how you remove the top lines. This is at the bash prompt...
Code:
$ echo x > file1

$ ( ( echo a ; sleep 30 ; echo b ) | tee -a file1 ) &
[1] 7000

$ a


$ sed -i 1d file1
sed: cannot rename ./sedCDnEEq: Permission denied

$ cat file1
x
a

$ awk '{a[NR]=$0}END{close(FILENAME);for(i=2;i<=NR;i++)print a[i]>FILENAME}' file1

$ cat file1
a

$ b

[1]+  Done                    ( ( echo a; sleep 30; echo b ) | tee -a file1 )

$ cat file1
a
b

$

In the example above, I created a file then submitted a background process to append to the file. Using sed -i to remove the first line didn't work, but awk worked okay.
 

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xzdiff

XZDIFF(1)							     XZ Utils								 XZDIFF(1)

NAME

       xzcmp, xzdiff, lzcmp, lzdiff - compare compressed files

SYNOPSIS

       xzcmp [cmp_options] file1 [file2]
       xzdiff [diff_options] file1 [file2]
       lzcmp [cmp_options] file1 [file2]
       lzdiff [diff_options] file1 [file2]

DESCRIPTION

       xzcmp  and  xdiff invoke cmp(1) or diff(1) on files compressed with xz(1), lzma(1), gzip(1), or bzip2(1).  All options specified are passed
       directly to cmp or diff.  If only one file is specified, then the files compared are file1 (which must have a suffix of	a  supported  com-
       pression  format)  and  file1 from which the compression format suffix has been stripped.  If two files are specified, then they are uncom-
       pressed if necessary and fed to cmp(1) or diff(1).  The exit status from cmp or diff is preserved.

       The names lzcmp and lzdiff are provided for backward compatibility with LZMA Utils.

SEE ALSO

       cmp(1), diff(1), xz(1), gzip(1), bzip2(1), zdiff(1)

BUGS

       Messages from the cmp(1) or diff(1) programs refer to temporary filenames instead of those specified.

Tukaani 							    2009-07-05								 XZDIFF(1)
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