(gawk.info.gz) Getline/File
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(gawk.info.gz) Getline
(gawk.info.gz) Getline/Variable/File
4.9.3 Using `getline' from a File
---------------------------------
Use `getline < FILE' to read the next record from FILE. Here FILE is a
string-valued expression that specifies the file name. `< FILE' is
called a "redirection" because it directs input to come from a
different place. For example, the following program reads its input
record from the file `secondary.input' when it encounters a first field
with a value equal to 10 in the current input file:
{
if ($1 == 10) {
getline < "secondary.input"
print
} else
print
}
Because the main input stream is not used, the values of `NR' and
`FNR' are not changed. However, the record it reads is split into
fields in the normal manner, so the values of `$0' and the other fields
are changed, resulting in a new value of `NF'.
According to POSIX, `getline < EXPRESSION' is ambiguous if
EXPRESSION contains unparenthesized operators other than `$'; for
example, `getline < dir "/" file' is ambiguous because the
concatenation operator is not parenthesized. You should write it as
`getline < (dir "/" file)' if you want your program to be portable to
all `awk' implementations.
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