Sh script to reduce version number in opkg status file

Question

I have written a script to reduce/lower the version number stored in opkg status file using small shell script, This will enable us to force the opkg to install same version of a Debian package again.

Versions stored in the opkg files are as follows,

Version: 00.03.00a002
Version: 201307001
Version: 201307001
Version: 3.12.002

And my script is as shown below, This script would run on the embedded board which is having busybox based sh shell. I have put bash tag to reach more people.

Script edits either 1st version number or 2nd version number..I didn't take third because sometimes that would contain alphanumeric value and I am uncomfortable with handling hex subtraction.

#!/bin/sh
#Small script to Lower firmware version 
OPKG_STATUS_FILE="/var/lib/opkg/status"
stamp=$(date +%s)
BACKUP_OPKG_STATUS_FILE="/var/lib/opkg/status_${stamp}"
#Creating backup file so that we can get back actual version if we want
cp ${OPKG_STATUS_FILE} ${BACKUP_OPKG_STATUS_FILE}
echo "${BACKUP_OPKG_STATUS_FILE} file created"
#clear original status file
:> ${OPKG_STATUS_FILE}
while IFS=' ' read -r line || [ -n "${line}" ];do
 ver_found=""
 ver_found=$(echo "${line}" | grep -i "Version")
 if [ ! -z "${ver_found}" ];then
 ver_extracted=""
 new_line=""
 for i in 1 2;do
 ver_extracted=$(echo "${line}" | grep -i "Version" | cut -d ':' -f 2 | cut -d '.' -f ${i})
 if [ ! -z "${ver_extracted}" ];then
 {
 #reduce version number
 if [ "${ver_extracted}" -gt 0 ];then
 new_version=$(printf "%02d %02d" "${ver_extracted}" "01" | awk '{ printf "%.0f", 1ドル - 2ドル }')
 new_line=$(echo ${line} | sed -e "s:${ver_extracted}:${new_version}:I")
 line="${new_line}"
 else
 continue
 fi
 break
 }
 fi
 done
 fi
 echo "${line}" >> "${OPKG_STATUS_FILE}"
done < "${BACKUP_OPKG_STATUS_FILE}"

I wanted to ask

1. if there is a better method for doing this.
2. One problem what I observed with my script is 03 is reduced and replaced with 2 instead of 02
   I need to keep versions digits same, any suggestion for that ?

• BCdotWEB: The problem you describe sounds like a bug, which would make this off-topic for CR.
• ART: how about better/simpler method any suggestions?

Answer 1

Since you're already using awk in there, it would be better to rewrite all the echo - grep - sed processing with a single awk. In particular, the entire while loop in the middle can be replaced with this:

awk -F '[:. ]' '/^Version: / {
 num1 = 3ドル;
 num2 = 4ドル;
 if (num1 > 0) {
 gsub(num1, num1 - 1);
 print;
 } else if (num2 > 0) {
 gsub(num2, num2 - 1);
 print;
 }
}
' "${BACKUP_OPKG_STATUS_FILE}" >> "${OPKG_STATUS_FILE}"

This produces slightly different (I think better) output than your original, and with the number of sub-processes greatly reduced, it's a lot more efficient.

• ART: this doesn't work on busybox shell. :( awk: cmd. line:2: Call to undefined function
• janos: Hm, that's probably because of the strtonum function I used. I removed it, it's probably not really needed (not for your example data anyway)