Add Shell.append_if_missing() helper

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.

[makermelissa-ai-assistant]

Adds Shell.append_if_missing(file, line) — the common "add a line only if it isn't already there" idiom that the installer scripts repeat constantly for /etc/modules, modprobe blacklists, and config.txt entries.

It's the Python equivalent of:

grep -qxF "line" file ||echo line >> file

Complements the existing reconfig() (which is uncomment-or-append for a regex pattern). append_if_missing is for the simpler exact-line case where you just want to guarantee a literal line is present without disturbing anything else.

Uses re.escape so lines containing regex metacharacters (e.g. dtoverlay=i2s-mmap) are matched literally rather than as patterns.

Context

Suggested by @makermelissa on adafruit/Raspberry-Pi-Installer-Scripts#398, where several converted installers each define a private copy of this helper. Landing it here lets those scripts share one implementation.

Testing

• ruff format + ruff check + reuse lint (pre-commit) all pass.
• Manually verified: no duplicate when the line is already present (anywhere in the file), appends when absent, and metacharacter-containing lines dedup correctly.

[makermelissa]

This is similar to reconfig, but it won't update an existing string.