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.
You can think of it as a Unix love-child of the split(1), tee(1), and xargs(1) commands.
It's usefulness might best be illustrated by an example. Suppose you have a file 'certs.pem' containing a number of x509 certificates in PEM format, and you wish to extract e.g., the subject and validity dates from each.
The openssl s_client(1) utility can only accept a single certificate at a time, so you'll have to first split the input into individual files containing exactly one cert, then repeatedly run the s_client(1) command against each file.
And, let's be honest, you probably have to google how to use sed(1) or awk(1) to extract subsequent blocks from a flip-flop pattern.
xpipe(1) can do the job for you in a single command:
$ <certs.pem xpipe -p '^-----END CERTIFICATE-----$' \ openssl x509 -noout -subject -dates notBefore=Aug 13 00:29:00 1998 GMT notAfter=Aug 13 23:59:00 2018 GMT subject= /C=US/O=GTE Corporation/OU=GTE CyberTrust Solutions, Inc./CN=GTE CyberTrust Global Root notBefore=Aug 1 00:00:00 1996 GMT notAfter=Dec 31 23:59:59 2020 GMT subject= /C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting cc/OU=Certification Services Division/CN=Thawte Server CA/emailAddressfirstname.lastname@example.org notBefore=Aug 1 00:00:00 1996 GMT notAfter=Dec 31 23:59:59 2020 GMT subject= /C=ZA/ST=Western Cape/L=Cape Town/O=Thawte Consulting cc/OU=Certification Services Division/CN=Thawte Premium Server CA/emailAddressemail@example.com [...]
For more details and examples, please see the manual page.
To install the command and manual page somewhere
make install; the Makefile defaults
to '/usr/local' but you can change the PREFIX:
$ make PREFIX=~ install
xpipe(1) was developed on a NetBSD 8.0 system. It was tested and confirmed to build and pass all tests on:
- NetBSD 8.0
- macOS 10.15.2
- RHEL 6.10
- RHEL 7.6
If you run into build/test issues, please email me.
NAME xpipe -- split input and feed it into the given utility SYNOPSIS xpipe [-Ic] [-J replstr] [-b bytes] [-n lines] [-p pattern] [utility [argument ...]] DESCRIPTION The xpipe command reads input from stdin and splits it by the given num- ber 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 occur- rence 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 execu- tion 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 argu- ments. This allows you to process input either in byte-, line-, or pattern-sepa- rated 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 exe- cute 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 pat- tern 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 out- put 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 repre- senting 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 can- not be found, xpipe exits with a value of 127; if utility cannot be exe- cuted, 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 <firstname.lastname@example.org> in January 2020. BUGS Please file bugs and feature requests by emailing the author.