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Debian – postgres docker container bash script not replacing variable in sed

In my dockerized container I am unable to replace a variable using ‘sed’.

These are my files:

myfile.sql

CREATE TABLE IF NOT EXISTS ${PG_TABLE}(...)

myscript.sh

#!/bin/sh
echo "variable1=${1}"
echo "variable2=${2}"
sed  -i "s/${$1}/$2/g" myfile.sql

run command

myscript.sh PG_TABLE "mytablename"

Actual:

  • echo variable1=PG_TABLE
  • echo variable2=mytablename
  • REPLACEMENT:
    CREATE TABLE IF NOT EXISTS (…)

Expected:

  • echo variable1=PG_TABLE
  • echo variable2=mytablename
  • REPLACEMENT
    CREATE TABLE IF NOT EXISTS mytablename(…)

This is supposed to replace the placeholder with my variable ‘mytablename’, but it just replaces it with empty string.

Maybe its because of my container alpine version.
This is my os.

my docker build operating system

cat /etc/os-release
  • PRETTY_NAME="Debian GNU/Linux 12 (bookworm)"
  • NAME="Debian GNU/Linux"
  • VERSION_ID="12"
  • VERSION="12 (bookworm)"
  • VERSION_CODENAME=bookworm
  • ID=debian
Tags:

2

Answers


  1. Chosen as BEST ANSWER
    0

    ok I made a mistake. The reason it didn't work is because I was expecting the arg to exist in my docker-compose file and it wasn't. Therefore the replacement was empty "". Adding in that arg

    docker-compose.yml

    ...
    build:
      context: .
      args:
       - PG_DB=${PG_DB}
       - PG_TABLE=${PG_TABLE} # Needed to pass variable to Dockerfile during

    Dockerfile

    # ...
FROM postgres
ARG PG_DB #  Need to recieve arg
ARG PG_TABLE

ADD seed.sql /docker-entrypoint-initdb.d/seed.sql

COPY script.sh .
RUN chmod +x script.sh

# Need to pass arg to script
RUN ./script.sh PG_DB "${PG_DB}" PG_TABLE "${PG_TABLE}"

  2. 0

    Issue is with sed placeholder.

    Use ${${1}} to match the placeholder in the myfile.sql

    Here’s the working solution, where running the container shows correct replacement.

    myscript.sh

    #!/bin/sh
echo "variable1=${1}"
echo "variable2=${2}"
echo "Running sed command..."
echo "sed -i "s/\${${1}}/${2}/g" /app/myfile.sql"
sed -i "s/${${1}}/${2}/g" /app/myfile.sql
cat /app/myfile.sql

    myfile.sql

    CREATE TABLE IF NOT EXISTS ${PG_TABLE}(...);

    Dockerfile

    FROM debian:bookworm

RUN apt-get update && apt-get install -y sed

COPY myfile.sql /app/myfile.sql
COPY myscript.sh /app/myscript.sh

WORKDIR /app

RUN chmod +x myscript.sh

CMD ["./myscript.sh", "PG_TABLE", "mytablename"]
    • docker build -t sed-replacement .
    • docker run –rm sed-replacement

    OUTPUT

    variable1=PG_TABLE
variable2=mytablename
Running sed command...
sed -i "s/${PG_TABLE}/mytablename/g" /app/myfile.sql
CREATE TABLE IF NOT EXISTS mytablename(...);
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