[[TOC]]
= !SysAdmin Tips =

== Renaming multiple files ==
{{{
for i in *.avi; do j=`echo $i | sed 's/find/replace/g'`; mv "$i" "$j"; done
}}}

{{{
for i in *.phtml; do mv $i ${i%.phtml}.php; done
}}}

== Deleting files matching a pattern ==
{{{
find opt/Products -name "*.pyc" -exec rm '{}' \;
}}}

== Sed: Stream Editor ==
Search/Replace:
{{{
sed 's/old/new/g' input.txt > output.txt
}}}
Faster:
{{{
sed '/old/ s/old/new/g' input.txt > output.txt
}}}

Do on a folder full of files:
{{{
#! /bin/sh
# Source files are saved as "filename.txt.bak" in case of error
# The '&&' after cp is an additional safety feature
for file in *.txt
do
cp $file $file.bak &&
sed 's/foo/bar/g' $file.bak >$file
done
}}}

Insert paragraph:
 * e.g. search for lines `#include <termios.h>' and then write:
{{{
#ifdef SYSV
#include <termios.h>
#else
#include <sgtty.h>
#endif
}}}

Now, for writing the same script on one line, the -e mechanism is needed... what follows each -e can be considered as an input line from a sed script file, so nothing kept us from doing:
{{{
sed -e '/#include <termios\.h>/{' \
-e 'i\' \
-e '#ifdef SYSV' \
-e 'a\' \
-e '#else\' \
-e '#include <sgtty.h>\' \
-e '#endif' \
-e '}'
}}}

1-liners:
 * http://sed.sourceforge.net/sed1line.txt

Tutorial:
 * http://sed.sourceforge.net/grabbag/tutorials/do_it_with_sed.txt

Collected resources:
 * http://sed.sf.net/

== Adding a swapfile ==
If you have a live system which you need to give extra swapspace too without a reboot, then can add a swapfile.

Note that a swapfile is much slower than a swap partition, which is -of course- slower than memory. The reason for this is to save the ship when the boat's going down, not increase preformance.

Create file:
{{{
dd if=/dev/zero of=/swapfile count=[size of swap, in 512B blocks]
}}}
Format it:
{{{
mkswap /swapfile -p 16384
}}}
Tell the kernel to use it at an lower priority (i.e. only use when swap parition is full):
{{{
swapon -p 16384 /swapfile 
}}}


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MaintenanceGuidelines