3.6 Command Strings

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Four fields hold executable commands: ExecStartPre, ExecStartPost, the command form of ExecReload, and HealthCheck. All four are parsed the same way.

3.6.1 Parsing #

The string is split on whitespace into an argv, with double quotes grouping. There is no shell — no expansion, no substitution, no globbing, and peinit never invokes one. A command that needs shell features is wrapped in a script.

Whitespace means exactly six characters: space, horizontal tab, line feed, carriage return, form feed and vertical tab. Every other Unicode whitespace code point is an ordinary argument character, which keeps the split independent of the Unicode version peinit was built against.

Double quotes group text into one argv element and are not retained in the result. Grouping may happen inside an argument, so --name="hello world" becomes the single entry --name=hello world. An empty quoted string is preserved as an empty argv entry.

Backslash has no escape semantics and is copied literally. A single quote is an ordinary character.

An empty or whitespace-only command is invalid, and so is an unclosed double quote.

3.6.2 The executable #

For all four fields, argv[0] is the executable path and begins with /. Relative names, empty names and PATH-searched execution are decode errors. Everything after argv[0] is an opaque string and is not path validated.

3.6.3 ExecReload signals #

ExecReload may instead name a signal, as signal:<NAME>. The name is an exact canonical Linux signal name. Numeric values, realtime signal expressions, aliases, lowercase spellings and names with surrounding whitespace are all invalid.

SIGKILL and SIGSTOP are invalid for reload, because a service cannot handle either as a request to re-read its configuration.

The accepted set is the standard non-realtime Linux signals other than those two:

SIGHUP, SIGINT, SIGQUIT, SIGILL, SIGTRAP, SIGABRT, SIGBUS, SIGFPE, SIGUSR1, SIGSEGV, SIGUSR2, SIGPIPE, SIGALRM, SIGTERM, SIGSTKFLT, SIGCHLD, SIGCONT, SIGTSTP, SIGTTIN, SIGTTOU, SIGURG, SIGXCPU, SIGXFSZ, SIGVTALRM, SIGPROF, SIGWINCH, SIGIO, SIGPWR, SIGSYS.

Names are validated when the definition is read and again before delivery, and mapped to host signal numbers at that point. ExecReload absent means SIGHUP.

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