NAME

xpipe — split input and feed it into the given utility

SYNOPSIS

DESCRIPTION

The xpipe command reads input from stdin and splits it by the given number of bytes, lines, or if matching the given pattern. It then invokes the given utility repeatedly, feeding it the generated data chunks as input.

OPTIONS

The following options are supported by xpipe:

-I

Do not write incomplete data.

-J replstr

When constructing the command to execute, replace the occurrence of replstr with the integer representing the number of invocation performed.

-b num

Split input every num bytes.

-c

Continue even if utility failed.

-n num

Split input every num lines.

-p pattern

Split input by the given pattern. See section PATTERNS for details.

DETAILS

xpipe conceptually combines some of the functionality of the split(1), tee(1), and xargs(1) utilities. That is, it allows for repeated execution of the given utitity, but unlike xargs(1), xpipe allows you to split the input and pipe it into the utility rather than passing it as arguments.

This allows you to process input either in byte-, line-, or pattern-separated chunks and pipe those chunks into the same tool without having to manually split the input or store data in temporary files.

Input processing is done sequentially: data is read up until the end of the given pattern (or until the given number of bytes or lines has been encountered); when that condition is encountered, utility is invoked and the data chunk is written into a pipe to that process; xpipe then waits for the process to complete, upon which it continues to read input.

If EOF is reached before the given condition is met, then xpipe will execute utility and pipe into it whatever data it encountered so far. This can be avoided by passing the -I flag, which leads to xpipe discarding any partial data without invoking utility (again or at all).

PATTERNS

When the -p flag is specified, xpipe will split input by the given pattern with each chunk including the pattern as the last bytes.

A pattern is, by and large, a simple, fixed string. That is, you cannot specify regular expressions or shell globs; all characters or bytes are matched verbatim with the exception of the following:

^

If the '^' character is specified at the beginning of the pattern, then it will anchor the pattern at the beginning of the line.

To match a literal '^' at the beginning of the line, escape the character using '^\^'. For example, to match a line beginning with the string ´^foo', you'd use the pattern '^\^foo'.

$

If the '$' character is specified at the end of the pattern (i.e., as the last character), then it will anchor the pattern at the end of the line.

To match a literal '$' at the end of the line, escape the character using '\$$'. For example, to match a line ending with 'foo', you'd use the pattern 'foo$'; To match a line ending with ´foo$', you'd use 'foo\$$'.

\n

This will match a new line (ASCII 10). The difference to '$' is that you can match a \n anywhere in your pattern, while a '$' will only match at the end of he line.

For example, to match a line ending in 'foo' followed by a line beginning with 'bar', you'd use the pattern ´foo\nbar'.

\t

This will match a tab character (ASCII 9).

For example, to match a line beginning with two tabs followed by the string 'foo', you'd use the pattern ´^\t\tfoo'.

COMMAND INVOCATION

xpipe will invoke the given utility with any subsequent arguments. If the -J flag is specified, then the given replstr in any of the arguments (including the utility itself) will be replaced with the number of the invocation.

Since I/O redirection is processed by the invoking shell, you'd have to invoke a new shell to allow for redirection to e.g. a per-invocation output file.

For example, to split the input into unique files ending in the given pattern:

<input xpipe -J % -p pattern /bin/sh -c "cat >%.out"

EXAMPLES

The following examples illustrate common usage of this tool.

To count the number of words in each paragraph of 'Don Quijote':

curl -s https://www.gutenberg.org/cache/epub/2000/pg2000.txt | \
        tr -d '^M' | \
        xpipe -p '^$' wc -w

To extract the subjects of all certificates in a standard PEM formatted x.509 trust bundle:

<certs.pem xpipe -p '^-----END CERTIFICATE-----$' \
        openssl x509 -noout -subject

To split a large, uncompressed log file into multiple, compressed files, named 1.gz, 2.gz, ... n.gz:

<logfile xpipe -n 1000 -J % /bin/sh -c "gzip >%.gz"

EXIT STATUS

The xpipe command exits with a value of 0 if no error occurs.

If the -c flag is passed, xpipe will exit with an integer value representing the total number of invocations of the utility that failed.

If the -c was not passed, then any failure in the execution of the utility leads to the termination of xpipe. That is, if the utility cannot be found, xpipe exits with a value of 127; if utility cannot be executed, xpipe exits with a value of 126; if utility terminated because of a signal, xpipe exits with a value of 125. If any other error occurs, xpipe exits with a value of 1.

SEE ALSO

split(1), tee(1), xargs(1)

HISTORY

xpipe was originally written by Jan Schaumann ⟨jschauma@netmeister.org⟩ in January 2020.

BUGS

Please file bugs and feature requests by emailing the author.