execl-envfile.md

title: The 66-tools Suite: execl-envfile author: Eric Vidal eric@obarun.org

66-tools

Software

obarun.org

execl-envfile

A mix of s6-envdir and importas. Reads files containing variable assignments in the given file/directory, adds the variables to the environment and then executes a program.

Interface

execl-envfile [ -h ] [ -v verbosity ] [ -l ] src prog

This program expects to find a regular file or a directory in src containing one or multiple key=value pair(s). It will parse that file, import the key=value and then exec the given prog with the modified environment. In case of directory for each file found it apply the same process. src can be an absolute or a relative path.

• It opens and reads a file.

• It parses that file.

• It imports the found key=value pair(s).

• It substitutes each corresponding key with value from that file.

• It unexports the variable(s) if requested.

• It execs prog with the modified environment.

Options

• -h: prints this help.

• -v verbosity: increases/decreases the verbosity of the command.

  • 1: only print error messages. This is the default.
  • 2: also print warning messages.
  • 3: also print tracing messages.
  • 4: also print debugging messages.

• -l: loose; do nothing and execute prog directly if src does not contain any regular file(s) or src does not exist.

File syntax

src is a text file or a directory containing lines of pairs with the syntax being: key = value Whitespace is permitted before and after key, and before or after value. Quoting is also possible.

Empty lines or lines containing only whitespace are ignored. Lines beginning with # (also after whitespace) are ignored and typically used for comments. Comments are not possible at the end of lines: key = value # comment is not a valid comment.

If val begin by a ! character: key=!value the key will be removed from the environment after the substitution.

Usage example

    #!/usr/bin/execlineb -P
    fdmove -c 2 1
    execl-envfile %%service_admconf%%/ntpd
    foreground { mkdir -p  -m 0755 ${RUNDIR} }
    execl-cmdline -s { ntpd ${CMD_ARGS} }

The equivalent with s6-envdir and importas would be:

    #!/usr/bin/execlineb -P
    fdmove -c 2 1
    s6-envdir %%service_admconf%%
    importas -u RUNDIR RUNDIR
    importas -u CMD_ARGS CMD_ARGS
    foreground { mkdir -p  -m 0755 ${RUNDIR} }
    execl-cmdline -s { ntpd ${CMD_ARGS} }

where %%service_admconf%% contains two named files RUNDIR and CMD_ARGS written with /run/openntpd and -d -s respectively.

Limits

src can not exceed more than 100 files. Each file can not contain more than 8191 bytes or more than 50 key=value pairs.