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 `ksh`, `zsh` and `bash`.

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.

The Windows shell supports only double quoting. All this implementation does is to surround by double quotes and escape internal double quotes by a backslash. As Windows path names cannot contain double quotes, this makes `shQuote` safe for use with `system` and with `shell` if the default shell is used.

It will usually be safe to use `shQuote` to quote arguments of a command, but because `system` does not use a shell, interpretation of quoted arguments is done by the run-time code of the executable.

### 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 <- "use the `-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")))

[Package base version 2.3.1 Index]