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Delete first 100 lines from a BIG File
Post 302657449 by drl on Sunday 17th of June 2012 06:22:14 PM
06-17-2012
Hi, Scrutinizer.
When was the last time you know that that happened to anyone? Most important *nix boxes will be backed up with a UPS. I think it is far more likely to fall prey to plain old user error.
However, I sometimes allow myself the luxury of following:
-- Unix philosophy - Wikipedia, the free encyclopedia
Best wishes ... cheers, drl
Quote:
It seems to me any solution should always make use a temporary intermediate file for safety reasons. If we read the whole file into memory and then write it back to the same file, we run the risk of losing the original in case of power failure during the write-back phase..
With a temporary file there is only mv involved, which is only a rename if the temporary file is in the same dir on the same file system, so a temporary file in the same directory instead of /tmp for example may be preferably. If we use /tmp for example for the intermediate file, a temporary rename to .bak of the original until the move from /tmp may be required and safest will probably be to keep the .bak until the user deletes it..
With a temporary file there is only mv involved, which is only a rename if the temporary file is in the same dir on the same file system, so a temporary file in the same directory instead of /tmp for example may be preferably. If we use /tmp for example for the intermediate file, a temporary rename to .bak of the original until the move from /tmp may be required and safest will probably be to keep the .bak until the user deletes it..
However, I sometimes allow myself the luxury of following:
Quote:
"Unix was not designed to stop its users from doing stupid things, as that would also stop them from doing clever things." - Doug Gwyn
Best wishes ... cheers, drl
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LEARN ABOUT DEBIAN
dbs-edit-patch
DBS-EDIT-PATCH(1) Debian Build System DBS-EDIT-PATCH(1) NAME
dbs-edit-patch - Edit a DBS patch SYNOPSIS
dbs-edit-patch [options] patch dbs-edit-patch -h|--help DESCRIPTION
dbs-edit-patch is script to generate or modify patches for Debian source-packages in DBS format. WARNING
dbs is deprecated, please switch to the `3.0 (quilt)' Debian source package format instead. See http://wiki.debian.org/Projects/Deb- Src3.0#FAQ for a short guide how to do it. OPTIONS
-h, --help Show summary of options. -t dir, --tmpdir=dir Directory for the temporary files, default is /tmp or if set $TMP. -s dir, --sourcedir=dir Top level directory of the debian-package source-tree, default is the present working directory. -P dir, --sourcepatchdir=dir Directory containing upstream patches. -T dir, --sourcetardir=dir Directory containing the upstream tarball. -p level, --strip=level Striplevel -p of patch (Option -p of diff(1)), accepted values are 0 and 1, default is 0. ENVIRONMENT VARIABLES
TMP Sets the directory for the temporary files, can be overridden with -t dir. debian/vars dbs-edit-patch will automatically use variables defined in the optional debian/vars file. When a file debian/vars.in exists and debian/vars either does not exist or is older than any of the following files: debian/vars.in, debian/changelog, debian/rules or debian/control, then dbs-edit-patch will try updating the vars file by running the following command make -f debian/rules -W debian/vars.in debian/vars EXAMPLES
Edit the 021_debian patch of Heimdal: ~/heimdal-0.3d> dbs-edit-patch -t/tmp 021_debian Extracting source heimdal-0.3d.tar.gz ... successful. Applying patch 001_replay ... successful. etc. Copying heimdal-0.3d to heimdal-0.3d-old ... successful. Applying patch 021_debian ... successful. Edit files under /tmp/021_debian/heimdal-0.3d as required, then put a short description into /tmp/021_debian/patch-description if desired, and finally execute /tmp/021_debian/dbs-update-patch to save the results. Technical note: dbs-edit-patch extracts all patches before 021_debian into /tmp/021_debian/heimdal-0.3d, copies the result to /tmp/021_debian/heimdal-0.3d-old, and applies the last patch 021_debian (if it exists). Also, it creates a shell script which will create the diff between the old and new directories: ~/heimdal-0.3d> ls -la /tmp/021_debian total 12 -rwxr-xr-x 1 bam users 112 Jan 31 13:31 dbs-update-patch* -rw-r--r-- 1 bam users 0 Jan 31 13:31 patch-description drwxr-xr-x 14 bam users 4096 Jan 31 13:31 heimdal-0.3d/ drwxr-xr-x 14 bam users 4096 Jan 31 13:31 heimdal-0.3d-old/ drwxr-xr-x 5 bam users 4096 Jan 31 13:31 .stampdir/ ~/heimdal-0.3d> cat /tmp/021_debian/dbs-update-patch #!/bin/sh -e cd "/tmp/021_debian" HOOK_DIR="/usr/src/heimdal/debian/dbs-hooks" test -d "$HOOK_DIR" && run-parts "$HOOK_DIR" --arg update-patch-prediff find -name "*.bak" -print0 | xargs -0 --no-run-if-empty rm find -name "*~" -print0 | xargs -0 --no-run-if-empty rm : > new_patch test ! -e patch-description || cp patch-description new_patch diff -ruN heimdal-0.3d-old heimdal-0.3d >> new_patch || test $? -eq 1 mv new_patch /usr/src/heimdal/debian/patches/021_debian test -d "$HOOK_DIR" && run-parts "$HOOK_DIR" --arg update-patch-postdiff SEE ALSO
diff(1), dbs(7), /usr/share/doc/dbs/ AUTHOR
DBS was written by Adam Heath, modified by Ben Collins, modified and packaged for Debian by Brian May. This manpage was generated by Andreas Metzler and modified by Robert Luberda. Debian February 15th, 2011 DBS-EDIT-PATCH(1)