shQuote {base}

R Documentation

Quote Strings for Use in OS Shells

Description

Quote a string to be passed to an operating system shell.

Usage

shQuote(string, type = c("sh", "csh", "cmd"))

Arguments

string	a character vector, usually of length one.
type	character: the type of shell. Partial matching is supported. "cmd" refers to the Windows NT shell, and is the default under Windows.

Details

The default type of quoting supported under Unix-alikes is that for the Bourne shell sh. If the string does not contain single quotes, we can just surround it with single quotes. Otherwise, the string is surrounded in double quotes, which suppresses all special meanings of metacharacters except dollar, backquote and backslash, so these (and of course double quote) are preceded by backslash. This type of quoting is also appropriate for bash, ksh and zsh.

The other type of quoting is for the C-shell (csh and tcsh). Once again, if the string does not contain single quotes, we can just surround it with single quotes. If it does contain single quotes, we can use double quotes provided it does not contain dollar or backquote (and we need to escape backslash, exclamation mark and double quote). As a last resort, we need to split the string into pieces not containing single quotes and surround each with single quotes, and the single quotes with double quotes.

References

Loukides, M. et al (2002) Unix Power Tools Third Edition. O'Reilly. Section 27.12.

http://www.mhuffman.com/notes/dos/bash_cmd.htm

See Also

Quotes for quoting R code.

sQuote for quoting English text.

Examples

test <- "abc$def`gh`i\\j"
cat(shQuote(test), "\n")
## Not run: system(paste("echo", shQuote(test)))
test <- "don't do it!"
cat(shQuote(test), "\n")

tryit <- paste("use the", sQuote("-c"), "switch\nlike this")
cat(shQuote(tryit), "\n")
## Not run: system(paste("echo", shQuote(tryit)))
cat(shQuote(tryit, type="csh"), "\n")

## Windows-only example.
perlcmd <- 'print "Hello World\n";'
## Not run: shell(paste("perl -e", shQuote(perlcmd, type="cmd")))

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