You can make list input more versatile by using modified list input. There are two modifiers that can be used with list input.

You can use modified list input to read the file shown below. This file contains the names of the 10 largest U.S. cities ranked in order based on their 2016 estimated population figures.

Notice that some of the values for city names contain embedded blanks and are followed by two blanks. Also, note that the values representing the population of each city are nonstandard numeric values (they contain commas).

The ampersand (&) modifier enables you to read character values that contain single embedded blanks. The & indicates that a character value that is read with list input might contain one or more single embedded blanks. The value is read until two or more consecutive blanks are encountered. The & modifier precedes a specified informat if one is used.

input Rank City &;

As shown below, you can use a LENGTH statement to define the length of City , and then add an & modifier to the INPUT statement to indicate that the values contain embedded blanks.

data sasuser.cityrank; 
   infile topten; 
   length City $ 12; 
   input Rank city &;

You can also read the values for City with the & modifier followed by the $w. informat, which reads standard character values, as shown below. When you do this, the w value in the informat determines the variable's length and should be large enough to accommodate the longest value.

The colon (:) modifier enables you to read nonstandard data values and character values that are longer than eight characters, but which contain no embedded blanks. The : indicates that values are read until a blank (or other delimiter) is encountered, and then an informat is applied. If an informat for reading character values is specified, the w value specifies the variable's length, overriding the default length.

Notice the values representing the 2016 population of each city in the raw data file below. Because they contain commas, these values are nonstandard numeric values.

In order to read these values, you can modify list input with the colon (:) modifier, followed by the COMMAw.d informat, as shown in the program below. Notice that the COMMAw.d informat does not specify a w value.

data sasuser.cityrank; 
   infile topten; 
   input Rank City & $12. 
         Pop86 : comma.;

Remember that list input reads each value until the next blank is detected. The default length of numeric variables is 8, so you do not need to specify a w value to indicate the length of a numeric variable.

This is different from using a numeric informat with formatted input. In that case, you must specify a w value in order to indicate the number of columns to be read.

At compile time, the informat $12. in the example below sets the length of City to 12 and stores this information in the descriptor portion of the data set. During the execution phase, however, the w value of 12 does not determine the number of columns that are read. This is different from the function of informats in the formatted input style.

data sasuser.cityrank; 
   infile topten; 
   input Rank City & $12. 
         Pop86 : comma.; 
run;

The & modifier indicates that the values for City should be read until two consecutive blanks are encountered. Therefore, the value NEW YORK is read from column 4 to column 11, a total of only 8 columns. When blanks are encountered in both columns 12 and 13, the value NEW YORK is written to the program data vector.

data sasuser.cityrank; 
   infile topten; 
   input Rank City & $12. 
         Pop86 : comma.; 
run;

The input pointer moves forward to the next nonblank column, which is column 14 in the first record. Now the values for Pop86 are read from column 14 until the next blank is encountered. The COMMAw.d informat removes the commas, and the value is written to the program data vector.

data sasuser.cityrank; 
   infile topten input Rank City & $12. 
         Pop86 : comma.; 
run;

Notice that the character values for City and Pop16 are stored correctly in the data set.

As you have seen, informats work differently in modified list input than they do in formatted input. With formatted input, the informat determines both the length of character variables and the number of columns that are read. The same number of columns are read from each record.

The informat in modified list input determines only the length of the variable, not the number of columns that are read. Here, the raw data values are read until two consecutive blanks are encountered.

input City & $12.;