AWK 内建变量FS,NF,NR,FNR,RT,RS,ORS,OFS

  看了网上好多关于AWK内建变量的文章，这里加上个人的理解和记忆，可以让大家掌握这些变量的基本用法。

FS 指定字段列分隔符（Font Space）

[~/AWK_learning]$ echo "111|222|333" | awk '{print $1}'111|222|333[~/AWK_learning]$ echo "111|222|333" | awk 'BEGIN{FS="|"}{print $1}'111

OFS 指定输出字段列分隔符（Output Font space）

[~/AWK_learning]$ echo "111 222 333" |awk 'BEGIN{OFS="|";}{print $1,$2,$3}'111|222|333

RS指定行分隔符 默认分隔符为\n（Row Space）

[~/AWK_learning]$  echo "111 222|333 444|555 666" | awk 'BEGIN{RS="|"}{print $0}'111 222333 444555 666

ORS指定输出行分隔符

[~/AWK_learning]$ awk 'BEGIN{ORS="|";}{print $0;}' test.txt111 222|333 444|555 666

RT 代指行分隔符

[~/AWK_learning]$  echo "111 222|333 444|555 666" | awk 'BEGIN{RS="|"}{print $0,RT}'111 222 |333 444 |555 666 |

NF 每行字段总数(Number of Font)

[~/AWK_learning]$ cat test.txt111 222333 444555 666[~/AWK_learning]$ awk '{print NF}' test.txt222[~/AWK_learning]$ awk '{print $NF}' test.txt222444666

NR 当前行数(Number of Row)

[~/AWK_learning]$ cat test.txt111 222333 444555 666 777[~/AWK_learning]$ awk '{print NR}' test.txt123[~/AWK_learning]$ awk '{print $NR}' test.txt111444777

FNR 当前文件行数(Number of Row in File)

  FNR与NR的区别用下面的例子可以很好的解释：

[~/AWK_learning/20171201]$ cat f1111 A222 B333 C[~/AWK_learning/20171201]$ cat f2i have 111he has 222she has 333[~/AWK_learning/20171201]$ awk '{print NR,$0}' f1 f21 111 A2 222 B3 333 C4 i have 1115 he has 2226 she has 333[~/AWK_learning/20171201]$ awk '{print FNR,$0}' f1 f21 111 A2 222 B3 333 C1 i have 1112 he has 2223 she has 333