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Michiel Borkent 2020-11-07 20:31:55 +01:00
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README.md
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@ -335,29 +335,8 @@ $ cat script.clj
### Input and output flags
In one-liners the `*input*` value may come in handy. It contains the input read from stdin as EDN by default. If you want to read in text, use the `-i` flag, which binds `*input*` to a lazy seq of lines of text. If you want to read multiple EDN values, use the `-I` flag. The `-o` option prints the result as lines of text. The `-O` option prints the result as lines of EDN values.
> **Note:** `*input*` is only available in the `user` namespace, on other namespaces use `*in*`.
The following table illustrates the combination of options for commands of the form
echo "{{Input}}" | bb {{Input flags}} {{Output flags}} "*input*"
| Input | Input flags | Output flag | `*input*` | Output |
|----------------|-------------|-------------|---------------|----------|
| `{:a 1}` <br> `{:a 2}` | | | `{:a 1}` | `{:a 1}` |
| hello <br> bye | `-i` | | `("hello" "bye")` | `("hello" "bye")` |
| hello <br> bye | `-i` | `-o` | `("hello" "bye")` | hello <br> bye |
| `{:a 1}` <br> `{:a 2}` | `-I` | | `({:a 1} {:a 2})` | `({:a 1} {:a 2})` |
| `{:a 1}` <br> `{:a 2}` | `-I` | `-O` | `({:a 1} {:a 2})` | `{:a 1}` <br> `{:a 2}` |
When combined with the `--stream` option, the expression is executed for each value in the input:
``` clojure
$ echo '{:a 1} {:a 2}' | bb --stream '*input*'
{:a 1}
{:a 2}
```
See [io-flags.md](doc/io-flags.md) for detailed documentation about input and
output flags.
### Current file path

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# Input and output flags
In one-liners the `*input*` value may come in handy. It contains the input read
from stdin as EDN by default. If you want to read in text, use the `-i` flag,
which binds `*input*` to a lazy seq of lines of text. If you want to read
multiple EDN values, use the `-I` flag. The `-o` option prints the result as
lines of text. The `-O` option prints the result as lines of EDN values.
> **Note:** `*input*` is only available in the `user` namespace, on other namespaces use `*in*`.
The following table illustrates the combination of options for commands of the form
echo "{{Input}}" | bb {{Input flags}} {{Output flags}} "*input*"
| Input | Input flags | Output flag | `*input*` | Output |
|----------------|-------------|-------------|---------------|----------|
| `{:a 1}` <br> `{:a 2}` | | | `{:a 1}` | `{:a 1}` |
| hello <br> bye | `-i` | | `("hello" "bye")` | `("hello" "bye")` |
| hello <br> bye | `-i` | `-o` | `("hello" "bye")` | hello <br> bye |
| `{:a 1}` <br> `{:a 2}` | `-I` | | `({:a 1} {:a 2})` | `({:a 1} {:a 2})` |
| `{:a 1}` <br> `{:a 2}` | `-I` | `-O` | `({:a 1} {:a 2})` | `{:a 1}` <br> `{:a 2}` |
When combined with the `--stream` option, the expression is executed for each value in the input:
``` clojure
$ echo '{:a 1} {:a 2}' | bb --stream '*input*'
{:a 1}
{:a 2}
```
When writing Clojure scripts that should be fully portable with the JVM, it is
not recommended to use in- and output flags and `*input*` since those are not
available in standard Clojure. Here is how you can rewrite:
## EDN input
Reading a single EDN value from stdin:
``` clojure
(ns script
(:require [clojure.edn :as edn]))
(edn/read *in*)
```
Reading multiple EDN values from stdin (the `-I` flag):
``` clojure
(ns script
(:require [clojure.edn :as edn]
[clojure.java.io :as io]))
(let [reader (java.io.PushbackReader. (io/reader *in*))]
(take-while #(not (identical? ::eof %)) (repeatedly #(edn/read {:eof ::eof} reader))))
```
## Text input
Reading text from stdin can be done with `(slurp *in*)`. To get a lazy seq of
lines (the `-i` flag), you can use:
``` clojure
(ns script
(:require [clojure.java.io :as io]))
(line-seq (io/reader *in*))
```
## Output
To print to stdout, use `println` for text and `prn` for EDN values.