read0

Read text from a file or process handle

read0 f           read0[f]
read0 (f;o;n)     read0[(f;o;n)]
read0 h           read0[h]
read0 (fifo;n)    read0[(fifo;n)]

where

• f is a file symbol
• (f;o;n) is a file descriptor
• h is a system or connection handle
• fifo is a communication handle to a Fifo
• n is a non-negative integer

returns character data from the source as follows.

File symbol

Returns the lines of the file as a list of strings. Lines are assumed delimited by either LF or CRLF, and the delimiters are removed.

q)`:test.txt 0:("hello";"goodbye")  / write some text to a file
q)read0`:test.txt
"hello"
"goodbye"

q)/ read 500000 lines, chunks of (up to) 100000 at a time
q)d:raze{read0(`:/tmp/data;x;100000)}each 100000*til 5

File descriptor

Returns n chars from the file, starting from the position o.

q)`:foo 0: enlist "hello world"
q)read0 (`:foo;6;5)
"world"

System or process handle

Returns a line of text from the source.

q)rl:{1">> ";read0 0}
q)rl`
>> xiskso
"xiskso"

Reading the console permits interactive input.

q)1">> ";a:read0 0
>> whatever
q)a[4+til 4]
"ever"

Fifo/named pipe

Returns n characters from the pipe. (Since V3.4 2016.05.31)

q)h:hopen`$":fifo:///etc/redhat-release"
q)read0(h;8)
"Red Hat "
q)read0(h;8)
"Enterpri"

---

Connection handles, File system, Interprocess communication
Q for Mortals §11.4.1 Reading and Writing Text Files