The toupper() function takes a single string as an argument and returns a copy of that string, with all the lowercase characters converted to uppercase. The nonalphabetic characters are left unchanged. The following example illustrates the usage of the toupper() function:

$ vi toupper1.awk

BEGIN    {
    str = "Linux is derived from Unix. Unix is oldest OS."
    upper_case_str = toupper(str)
    print "Original String : ", str
    print "Uppercase String : ", upper_case_str
}

$ awk -f toupper1.awk

The output of the execution of the previous code is as follows:

Original String :  Linux is derived from Unix. Unix is oldest OS.
Uppercase String :  LINUX IS DERIVED FROM UNIX. UNIX IS OLDEST OS.

Similarly, in our next example, we convert the contents of our emp.dat employee database file to uppercase using the toupper() function, as follows:

$ awk '{ printf("%s
", toupper($0)) }' emp.dat

The output of the execution of the previous code is as follows:

JACK    SINGH   9857532312  [email protected]      M   HR      2000
JANE    KAUR    9837432312  [email protected]      F   HR      1800
EVA     CHABRA  8827232115  [email protected]       F   LGS     2100
AMIT    SHARMA  9911887766  [email protected]      M   LGS     2350
JULIE   KAPUR   8826234556  [email protected]     F   OPS     2500
ANA     KHANNA  9856422312  [email protected]    F   OPS     2700
HARI    SINGH   8827255666  [email protected]      M   OPS     2350
VICTOR  SHARMA  8826567898  [email protected]    M   OPS     2500
JOHN    KAPUR   9911556789  [email protected]      M   HR      2200
BILLY   CHABRA  9911664321  [email protected]      M   LGS     1900
SAM     KHANNA  8856345512  [email protected]     F   LGS     2300
GINNY   SINGH   9857123466  [email protected]     F   HR      2250
EMILY   KAUR    8826175812  [email protected]     F   OPS     2100
AMY     SHARMA  9857536898  [email protected]    F   OPS     2500
VINA    SINGH   8811776612  [email protected]      F   LGS     2300