jc JSONifies the output of many CLI tools and file-types for easier parsing in scripts. jc accepts piped input from \fBSTDIN\fP and outputs a JSON representation of the previous command's output to \fBSTDOUT\fP. Alternatively, the "Magic" syntax can be used by prepending jc to the command to be converted. Options can be passed to jc immediately before the command is given. (Note: "Magic" syntax does not support shell builtins or command aliases)
Any fatal errors within jc will generate an exit code of \fB100\fP, otherwise the exit code will be \fB0\fP. When using the "Magic" syntax (e.g. \fBjc ifconfig eth0\fP), jc will store the exit code of the program being parsed and add it to the jc exit code. This way it is easier to determine if an error was from the parsed program or jc.
You can specify custom colors via the \fBJC_COLORS\fP environment variable. The \fBJC_COLORS\fP environment variable takes four comma separated string values in the following format:
Most parsers load all of the data from \fBSTDIN\fP, parse it, then output the entire JSON document serially. There are some streaming parsers (e.g. \fBls-s\fP and \fBping-s\fP) that immediately start processing and outputing the data line-by-line as JSON Lines (aka NDJSON) while it is being received from \fBSTDIN\fP. This can significantly reduce the amount of memory required to parse large amounts of command output (e.g. \fBls -lR /\fP) and can sometimes process the data more quickly. Streaming parsers have slightly different behavior than standard parsers as outlined below.
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Note: Streaming parsers cannot be used with the "magic" syntax
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\fBIgnoring Errors\fP
You may want to ignore parsing errors when using streaming parsers since these may be used in long-lived processing pipelines and errors can break the pipe. To ignore parsing errors, use the \fB-q\fP cli option or the \fBquiet=True\fP argument with the \fBparse()\fP function. This will add a \fB_meta\fP object to the JSON output with a \fBsuccess\fP attribute. If \fBsuccess\fP is \fBtrue\fP, then there were no issues parsing the line. If \fBsuccess\fP is \fBfalse\fP, then a parsing issue was found and \fBerror\fP and \fBline\fP fields will be added to include a short error description and the contents of the unparsable line, respectively:
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Successfully parsed line with \fB-q\fP option:
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{
"command_data": "data",
"_meta": {
"success": true
}
}
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Unsuccessfully parsed line with \fB-q\fP option:
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{
"_meta": {
"success": false,
"error": "error parsing line",
"line": "original line data"
}
}
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\fBUnbuffering Output\fP
Most operating systems will buffer output that is being piped from process to process. The buffer is usually around 4KB. When viewing the output in the terminal the OS buffer is not engaged so output is immediately displayed on the screen. When piping multiple processes together, though, it may seem as if the output is hanging when the input data is very slow (e.g. \fBping\fP):
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$ ping 1.1.1.1 | jc --ping-s | jq
<slow output>
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This is because the OS engages the 4KB buffer between \fBjc\fP and \fBjq\fP in this example. To display the data on the terminal in realtime, you can disable the buffer with the \fB-u\fP (unbuffer) cli option:
Local parser plugins are standard python module files. Use the \fBjc/parsers/foo.py\fP parser as a template and simply place a \fB.py\fP file in the \fBjcparsers\fP subfolder.
Local plugin filenames must be valid python module names, therefore must consist entirely of alphanumerics and start with a letter. Local plugins may override default plugins.
Note: The application data directory follows the XDG Base Directory Specification
\fBLocale:\fP For best results set the \fBLANG\fP locale environment variable to \fBC\fP or \fBen_US.UTF-8\fP. For example, either by setting directly on the command-line:
or by exporting to the environment before running commands:
\fB$ export LANG=C\fP
\fBTimezones:\fP Some parsers have calculated epoch timestamp fields added to the output. Unless a timestamp field name has a \fB_utc\fP suffix it is considered naive. (i.e. based on the local timezone of the system the \fBjc\fP parser was run on).
If a UTC timezone can be detected in the text of the command output, the timestamp will be timezone aware and have a \fB_utc\fP suffix on the key name. (e.g. \fBepoch_utc\fP) No other timezones are supported for aware timestamps.
