Shell script runs diffrently based on working directory.

Question

I have a script which runs differently based on current working directory. Basically it processes an .ini file and takes parameters from it and runs mysql backup.

Script is running as root user.

When I run it with working directory as /root. It exits with error. The .ini file parameters do not reflect in script.

When I do cd / then run it, it works fine.

Here is the function that seems to fail.

get_param()
{

 for line in `cat ${PARAMETERSFILE}`
 do

    if [ "${ISFOUND}" != "true" -a "`echo ${line} | grep ${STAG} | grep -v grep | wc -l`" == "1" ]
   then
     ISFOUND="true"
fi

    if [ "${ISFOUND}" == "true" -a "`echo ${line} | grep ${ETAG} | grep -v grep | wc -l`" == "1" ]
  then
     ISFOUND="false"
fi
if [ "${ISFOUND}" == "true" -a "`echo ${line} | grep ${STAG} | grep -v grep | wc -l`" != "1" ]
   then
    key="`echo ${line} | sed 's/=/ /' | awk '{print $1}'`"
    val="`echo ${line} | sed 's/=/ /' | awk '{print $2}'`"
    cmd="${key}=\"${val}\""
    eval ${cmd}
fi
 done
}

Some variables are as below:

STAG="\[backup\]"
ETAG="\/backup\]"
ISFOUND="false"

ini file is as below

[help]
 backupdir="Backup Home Directory "
 user="MySQL Database  Username"
 password="MySQL Database Password"
 retentioPeriodMinutes="Retention Period of Backup (e.g. 1440= 1 day)"
 memory="Dedicated RAM (Mbyte)"
[/help]

[backup]
 backupdir=/opt/backupdb
 user="root"
 password="xyz"
[/backup]

[restore]
 backupdir=/opt/backupdb
 user="root"
 password="xyz"
 memory="1024"
[/restore]

[houseKeeping]
 backupdir=/opt/backupdb
 retentioPeriodMinutes=10080
[/houseKeeping]

Below is the output while running with sh -xv. It seems pipe is not working as it should when current directory is /root

+ for line in '`cat ${PARAMETERSFILE}`'
echo ${line} | grep ${STAG} | grep -v grep | wc -l
++ grep '\[backup\]'
++ grep -v grep

++ wc -l
+ '[' false '!=' true -a 0 == 1 ']'
echo ${line} | grep ${ETAG} | grep -v grep | wc -l
++ grep '\/backup\]'
++ echo '[help]'
++ grep -v grep
++ wc -l

+ '[' false == true -a 0 == 1 ']'
echo ${line} | grep ${STAG} | grep -v grep | wc -l

++ grep -v grep
++ grep '\[backup\]'
++ echo '[help]'
++ wc -l

Here is same output when working directory is /

+ for line in '`cat ${PARAMETERSFILE}`'
echo ${line} | grep ${STAG} | grep -v grep | wc -l
++ grep '\[backup\]'
++ grep -v grep
++ echo '[help]'

+ '[' false '!=' true -a 0 == 1 ']'
echo ${line} | grep ${ETAG} | grep -v grep | wc -l
++ grep '\/backup\]'

++ grep -v grep
++ wc -l
++ echo '[help]'
+ '[' false == true -a 0 == 1 ']'
echo ${line} | grep ${STAG} | grep -v grep | wc -l
++ echo '[help]'
++ grep -v grep
++ grep '\[backup\]'

++ wc -l

Answer 1

I see at least one mistake that could explain the problem. I haven't reviewed your script in detail. Look at what this line does:

  for line in `cat ${PARAMETERSFILE}`

1. Take the value of the variable PARAMETERSFILE.
2. Split that value at whitespace — this results in a single word if the value contains only “ordinary” characters.
3. Perform filename expansion a.k.a. globbing on each word. This still results in a single word if the value of the variable contains only “ordinary” characters.
4. Run cat on the specified file.
5. Read the output of cat, since this is a command substitution.
6. Split the output of the command at whitespace. This time the string to split contains many newlines and a few spaces; the resulting words are [help], backupdir="Backup, Home, Directory, ", user="MySQL, Database, Username", …
7. Perform filename expansion a.k.a. globbing on each word.

This time some of the words contain wildcards so they will be interpreted as a glob pattern. If the pattern matches no file, it's left as is. If the pattern matches at least one file, it's replaced by the list of matching file.

A string like [help] is a glob pattern that four possible matches one-character filenames: h, e, l, p. So if you run the script in a directory that contains no file by any of these names, the word [help] remains intact, but if e.g. the current directory contains a file called h then [help] is replaced by h.

for line in … does not split the input into lines. The easiest way to do that is

while IFS= read -r line; do
  …
done <"$PARAMETERSFILE"

IFS= read -r line reads exactly one line, with no character other than newline being special. If you want to strip leading and trailing whitespace, remove IFS=. If you want to allow backslash to serve as a line continuation character (i.e. backslash at the end of a line ignores the following newline), remove -r.