Bash: quoting a string inside an array

Question

In a Bash script I need to execute a command which takes the list of the existing databases from PostgreSQL:

getdblist_cmd=(sudo -u $backup_user $psql -p $pgsql_port -U $pgsql_user -d postgres -q -t -c 'SELECT datname from pg_database')

# Get databases list
msg
msg "================================================================="
msg "Getting databases list ..."
dblist=`"${getdblist_cmd[@]}"`
status=$?
if [ "$status" -ne "0" ]; then
    return $status
fi

This works but I need to exclude the template0 database, but this does not work:

getdblist_cmd=(sudo -u $backup_user $psql -p $pgsql_port -U $pgsql_user -d postgres -q -t -c 'SELECT datname from pg_database WHERE datname != \'template0\')'

# Get databases list
msg
msg "================================================================="
msg "Getting databases list ..."
dblist=`"${getdblist_cmd[@]}"`
status=$?
if [ "$status" -ne "0" ]; then
    return $status
fi

It returns:

root@postgres /u/l/sbin# ./pgsql-backup-full-func.sh
./pgsql-backup-full-func.sh: line 145: unexpected EOF while looking for matching `''
./pgsql-backup-full-func.sh: line 187: syntax error: unexpected end of file

I know that no escaping is possible for single quotes in Bash, so how I can manage this?

Did you forget the opening single quote ' in your second copy of the script to stackoverflow? I feel like a single quote is missing before SELECT... — Mathieu CAROFF
– Mathieu CAROFF, Commented Feb 25, 2020 at 14:23

chepner · Accepted Answer · 2020-02-25 14:25:49Z

1

Stop using arrays when you should be using functions.

getdblist_cmd () {
  sudo -u "$backup_user" "$psql" -p "$pgsql_port" -U "$pgsql_user" -d postgres -q -t -c "SELECT datname from pg_database WHERE datname != 'template0'"
}

# Get databases list
msg
msg "================================================================="
msg "Getting databases list ..."
dblist=$(getdblist_cmd)
status=$?
if [ "$status" -ne "0" ]; then
    return $status
fi

answered Feb 25, 2020 at 14:25

chepner

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Comments

Mathieu CAROFF · Accepted Answer · 2020-02-25 14:30:50Z

0

I guess you have a few options --

Using double quotes

getdblist_cmd=(sudo -u $backup_user $psql -p $pgsql_port -U $pgsql_user -d postgres -q -t -c "SELECT datname from pg_database WHERE datname != 'template0'")

Using one more variable

sql_query='SELECT datname from pg_database WHERE datname != '\''template0'\'
getdblist_cmd=(sudo -u $backup_user $psql -p $pgsql_port -U $pgsql_user -d postgres -q -t -c $sql_query)

answered Feb 25, 2020 at 14:30

Mathieu CAROFF

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1 Comment

glenn jackman Over a year ago

Yes, you cannot put a single quote in a single quoted string

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