Archive for the Shell Scripting category
Version comparison using rpm
Posted on Thu, Feb 20, 2025 at 11:35 by Hubertus A. Haniel
I have been playing a little bit with ChatGPT and its code generators and while doing this I stumbled across this. I wrote about versiion comparison in a previos post which is sort of a common thing that keeps coming up and I have used the function that I refer to there lots of times. It seems that rpm actually has a build in function to do this which returns result codes so you can refer to this with a function like this but obviously it will not work on other platforms and it seems that this has not been available on all rpm versions but I do not know when it was introduced:
compare_rpm_versions() {
local version1="$1"
local version2="$2"
if [[ -z "$version1" || -z "$version2" ]]; then
printf "Error: Two versions must be provided\n" >&2
return 1
fi
if ! command -v rpm &>/dev/null; then
printf "Error: rpm command not found\n" >&2
return 2
fi
if rpm --eval "%{lua: print(rpm.vercmp('$version1', '$version2'))}" &>/dev/null; then
local result; result=$(rpm --eval "%{lua: print(rpm.vercmp('$version1', '$version2'))}")
case "$result" in
1) printf "%s is newer than %s\n" "$version1" "$version2"; return 0 ;;
0) printf "%s and %s are identical\n" "$version1" "$version2"; return 0 ;;
-1) printf "%s is older than %s\n" "$version1" "$version2"; return 0 ;;
*) printf "Error: Unexpected comparison result: %s\n" "$result" >&2; return 3 ;;
esac
else
printf "Error: Failed to compare versions\n" >&2
return 4
fi
}
Edited on: Wed, Jun 04, 2025 15:00Posted in HowTo (RSS), Packaging (RPM) (RSS), Shell Scripting (RSS), System - Linux (RSS)
Colour output in your scripts
Posted on Wed, Aug 02, 2023 at 13:03 by Hubertus A. Haniel
On Linux I have been using tput to produce colours in my output but then I noticed the other day that this does not actually seem to work on Solaris but I am not sure why so I had to resort to the old fashioned way of using escape sequences. This works perfectly fine in Linux:
#!/bin/bash
GREEN=$(tput setaf 2)
RED=$(tput setaf 1)
YELLOW=$(tput setaf 3)
NOCOL=$(tput sgr0)
echo "This works in Linux...."
echo "This is ${GREEN} Green${NOCOL} in Green"
echo "This is ${RED} Red${NOCOL} in Red"
echo "This is ${YELLOW} Yellow${NOCOL} in Yellow"
echo ""
So on Solaris this would be done like this (And this also works on
Linux):
#!/bin/bash
GREEN="\033[0;32m"
RED="\033[0;31m"
YELLOW="\033[0;33m"
NOCOL="\033[0m"
echo "This works in Linux and Solaris...."
echo -e "This is ${GREEN} Green${NOCOL} in Green"
echo -e "This is ${RED} Red${NOCOL} in Red"
echo -e "This is ${YELLOW} Yellow${NOCOL} in Yellow"
So I guess I am going to have to stick to the second method to make my stuff work across platforms - From the script bits above you can see that a font effect is turned on with a code and you will have you will have to use a reset code "\033[0m" to turn it back off. The \033 ANSI escape sequence has a lot of codes to go in hand with it to do all sort of clever effects.
echo -e "\033[31;1;4mHello\033[0m"
This example above has a comma separated list of codes so you got 31 for red, 1 for bold and 4 for underline and all this is cleared again with 0
This is a table that lists all the effect codes:
| Code | Effect | Note |
|---|---|---|
| 0 | Reset / Normal | all attributes off |
| 1 | Bold or increased intensity | |
| 2 | Faint (decreased intensity) | Not widely supported. |
| 3 | Italic | Not widely supported. Sometimes treated as inverse. |
| 4 | Underline | |
| 5 | Slow Blink | less than 150 per minute |
| 6 | Rapid Blink | MS-DOS ANSI.SYS; 150+ per minute; not widely supported |
| 7 | [[reverse video]] | swap foreground and background colors |
| 8 | Conceal | Not widely supported. |
| 9 | Crossed-out | Characters legible, but marked for deletion. Not widely supported. |
| 10 | Primary(default) font | |
| 11–19 | Alternate font |
Select alternate font n-10
|
| 20 | Fraktur | hardly ever supported |
| 21 | Bold off or Double Underline | Bold off not widely supported; double underline hardly ever supported. |
| 22 | Normal color or intensity | Neither bold nor faint |
| 23 | Not italic, not Fraktur | |
| 24 | Underline off | Not singly or doubly underlined |
| 25 | Blink off | |
| 27 | Inverse off | |
| 28 | Reveal | conceal off |
| 29 | Not crossed out | |
| 30–37 | Set foreground color | See color table below |
| 38 | Set foreground color |
Next arguments are 5;<n> or 2;<r>;<g>;<b>,
see below
|
| 39 | Default foreground color | implementation defined (according to standard) |
| 40–47 | Set background color | See color table below |
| 48 | Set background color |
Next arguments are 5;<n> or 2;<r>;<g>;<b>,
see below
|
| 49 | Default background color | implementation defined (according to standard) |
| 51 | Framed | |
| 52 | Encircled | |
| 53 | Overlined | |
| 54 | Not framed or encircled | |
| 55 | Not overlined | |
| 60 | ideogram underline | hardly ever supported |
| 61 | ideogram double underline | hardly ever supported |
| 62 | ideogram overline | hardly ever supported |
| 63 | ideogram double overline | hardly ever supported |
| 64 | ideogram stress marking | hardly ever supported |
| 65 | ideogram attributes off | reset the effects of all of 60-64 |
| 90–97 | Set bright foreground color | aixterm (not in standard) |
| 100–107 | Set bright background color | aixterm (not in standard) |
The table below lists the basic 8bit color table which should be sufficient for most cases - there are plenty of other sources to give you 256 colours but in most cases that would not be required
|
|
Posted in HowTo (RSS), Shell Scripting (RSS), System - AIX (RSS), System - Linux (RSS), System - Solaris (RSS)
Compare versions in bash - vercomp {}
Posted on Fri, Jun 24, 2022 at 17:23 by Hubertus A. Haniel
I have taken this from https://stackoverflow.com/a/4025065/1763937 and it can also be found at https://github.com/f-o-a-m/cliquebait/blob/master/vercomp.bash
I have put a copy of it here for my own reference mostly as I think this is a really good pice of code and I have used it in a few scripts now:
#!/bin/bash
vercomp () {
if [[ $1 == $2 ]]
then
return 0
fi
local IFS=.
local i ver1=($1) ver2=($2)
# fill empty fields in ver1 with zeros
for ((i=${#ver1[@]}; i<${#ver2[@]}; i++))
do
ver1[i]=0
done
for ((i=0; i<${#ver1[@]}; i++))
do
if [[ -z ${ver2[i]} ]]
then
# fill empty fields in ver2 with zeros
ver2[i]=0
fi
if ((10#${ver1[i]} > 10#${ver2[i]}))
then
return 1
fi
if ((10#${ver1[i]} < 10#${ver2[i]}))
then
return 2
fi
done
return 0
}
testvercomp () {
vercomp $1 $2
case $? in
0) op='=';;
1) op='>';;
2) op='<';;
esac
if [[ $op != $3 ]]
then
echo "FAIL: Expected '$3', Actual '$op', Arg1 '$1', Arg2 '$2'"
else
echo "Pass: '$1 $op $2'"
fi
}
# Run tests
# argument table format:
# testarg1 testarg2 expected_relationship
echo "The following tests should pass"
while read -r test
do
testvercomp $test
done << EOF
1 1 = 2.1 2.2 < 3.0.4.10 3.0.4.2 > 4.08 4.08.01 < 3.2.1.9.8144 3.2 > 3.2 3.2.1.9.8144 < 1.2 2.1 < 2.1 1.2 > 5.6.7 5.6.7 = 1.01.1 1.1.1 = 1.1.1 1.01.1 = 1 1.0 = 1.0 1 = 1.0.2.0 1.0.2 = 1..0 1.0 = 1.0 1..0 = EOF echo "The following test should fail (test the tester)" testvercomp 1 1 '>'
Now when you run the code:
$ . ./vercomp The following tests should pass Pass: '1 = 1' Pass: '2.1 < 2.2' Pass: '3.0.4.10 > 3.0.4.2' Pass: '4.08 < 4.08.01' Pass: '3.2.1.9.8144 > 3.2' Pass: '3.2 < 3.2.1.9.8144' Pass: '1.2 < 2.1' Pass: '2.1 > 1.2' Pass: '5.6.7 = 5.6.7' Pass: '1.01.1 = 1.1.1' Pass: '1.1.1 = 1.01.1' Pass: '1 = 1.0' Pass: '1.0 = 1' Pass: '1.0.2.0 = 1.0.2' Pass: '1..0 = 1.0' Pass: '1.0 = 1..0' The following test should fail (test the tester) FAIL: Expected '>', Actual '=', Arg1 '1', Arg2 '1'Edited on: Mon, Oct 10, 2022 12:43
Posted in Shell Scripting (RSS)
function cleanexit {} - Clean your shit!
Posted on Mon, Jun 20, 2022 at 11:42 by Hubertus A. Haniel
When writing shell scripts in bash that create temporary files I prefer to stick a clean exit function at the top of the script that runs the clean up no matter how the script exits - this should even remove files when the script got interrupted:
function cleanexit
{
rm -f /var/tmp/tmpfile
}
trap cleanexit INT QUIT TERM EXIT
Let me know if you have a better idea!
Edited on: Wed, Aug 02, 2023 14:36Posted in HowTo (RSS), Shell Scripting (RSS), System - AIX (RSS), System - Linux (RSS), System - Solaris (RSS)
Welcome - Notes from a Linux/Unix Engineer
Posted on Tue, Jun 01, 2010 at 11:11 by Hubertus A. Haniel
I used to collect notes documents and HOWTO's at http://www.rootunix.org which are now archived at http://www.unixcook.com/old-unix-docs/ as it was difficult to maintain and I got lazy with it. I have come across a cross-platform blog software called Thingamablog which is written in Java so it works on Windows and Unix and I am hoping that it will enable me to publish useful notes at a quicker pace with not a lot of messing around.
We will see how successful that will be....
Posted in Automation (RSS), HowTo (RSS), Packaging (RPM) (RSS), Shell Scripting (RSS), System - AIX (RSS), System - Apple / OSX (RSS), System - Linux (RSS), System - Solaris (RSS), System - Windows (RSS), Virtualization (RSS)
