使用bash(版本4+)的一种方法:

foo=bar
echo "${foo^}"

打印:

Bar

这里只是为了好玩:

foo="bar";    

echo $foo | awk '{$1=toupper(substr($1,0,1))substr($1,2)}1'
# or
echo ${foo^}
# or
echo $foo | head -c 1 | tr [a-z] [A-Z]; echo $foo | tail -c +2
# or
echo ${foo:1} | sed -e 's/^./\B&/'

它也可以在纯bash中使用bash-3.2完成:

# First, get the first character.
fl=${foo:0:1}

# Safety check: it must be a letter :).
if [[ ${fl} == [a-z] ]]; then
    # Now, obtain its octal value using printf (builtin).
    ord=$(printf '%o' "'${fl}")

    # Fun fact: [a-z] maps onto 0141..0172. [A-Z] is 0101..0132.
    # We can use decimal '- 40' to get the expected result!
    ord=$(( ord - 40 ))

    # Finally, map the new value back to a character.
    fl=$(printf '%b' '\'${ord})
fi

echo "${fl}${foo:1}"

据我所知，这是POSIX sh兼容的。

upper_first.sh:

#!/bin/sh

printf "$1" | cut -c1 -z | tr -d '\0' | tr [:lower:] [:upper:]
printf "$1" | cut -c2-

Cut -c1 -z以\0而不是\n结束第一个字符串。它被tr -d '\0'删除。它也可以省略-z并使用tr -d '\n'来代替，但如果字符串的第一个字符是换行符，则会中断。

用法:

$ upper_first.sh foo
Foo
$

在函数中:

#!/bin/sh

function upper_first ()
{
    printf "$1" | cut -c1 -z | tr -d '\0' | tr [:lower:] [:upper:]
    printf "$1" | cut -c2-
}

old="foo"
new="$(upper_first "$old")"
echo "$new"

$ foo="bar";
$ foo=`echo ${foo:0:1} | tr  '[a-z]' '[A-Z]'`${foo:1}
$ echo $foo
Bar

Posix兼容，子进程更少:

v="foo[Bar]"
printf "%s" "${v%"${v#?}"}" | tr '[:lower:]' '[:upper:]' && printf "%s" "${v#?}"
==> Foo[Bar]